Inflammmation is one of the most widespread and obvious dirty tactics. Anyone can do it, but it takes some skill to be really good at it. This involves not only being more effective with it, but doing it in ways that many observers won't consider insulting, at least if they already agree with your message. This can be used in an online argument to bait your opponent into flaming you in retaliation, and then having the moderators censor them and not you.
First, there's a different between flaming and inflaming. Flaming involves directly and explicitly insulting your opponent, especially with the use of all caps or profanity, and is actually a subset of inflaming. Inflaming is about making your opponent angry. And so flaming is actually the least effective form of inflaming, being suicidal more often than not - most times you're the first to swear at an opponent in an online argument, everyone else in the conversation instantly dismisses you and downvotes you if the forum has such a mechanic. You may even be censored by the moderators. The result is that you actually make your opponent feel better. Unfortunately for reasonable debaters, there are ways to inflame someone in much more subtle - and much more powerful - ways. Here are some techniques I've learned from seeing skilled assholes do this on the internet:
Strike at a point you know is sensitive for your opponent, but wouldn't be sensitive for most people. For an example, I'll look at a scene from Doki Doki Literature Club (don't worry, no real spoilers here). On day 2, when the literature club members share their poems with each other for the first time, Natsuki and Yuri greatly dislike each other's poems and get into a heated argument about it. Background info: Yuri is shy and into fantasy and horror novels with deep worldbuilding, and this is reflected in her poetry, which uses more big words and metaphors with no clear subject or message. Natsuki prefers simpler language and more concrete themes with an explicit message. Also, Natsuki is cute (this is not coming from me; all the other characters agree on this), but firmly denies it. Their criticism of each other's poems starts something like this:
Natsuki: "(What's with this language?)"
Yuri: "Did you say something?"
Natsuki: "Oh, it's nothing. I guess you could say it's fancy."
Yuri: "Thanks. Yours is... cute, I guess..."
Natsuki: "Cute? Did you completely miss the symbolism or something? It's clearly about the feeling of giving up! How can that be cute?"
The argument goes on for quite a while longer, but I'll stop here. In the last two lines, both of them used this technique, intentionally or not. Yuri used it by calling Natsuki's poem cute. It's clear to everyone at this point that Natsuki doesn't like to be seen as cute, so despite how Yuri's commment is ostensibly a compliment, it's actually about the most inflammatory thing she could have said at that point. Natsuki, for her part, uses the technique with "Did you completely miss the symbolism or something"? Since it's known that Yuri prefers more abstract and complicated imagery, questioning her ability to understand the symbolism of even a simple poem that isn't hers is the most threatening criticism one could level against her. But since neither of these are sensitive points for most people, the other characters don't realize just how mean the girls are being to each other. If you can learn to stealth-flame people like this, you can very often make it look like the opponent is the one being mean, if they can't find a similarly clever response and resort to overt flaming to retaliate.
Metadebating. This is a term I've coined for a nasty technique where you comment on how the debate is going; for example, saying "No offense, but you're doing a very poor job arguing for your claim" or "Hopefully this time you can make a less fallacious argument" after giving a rebuttal. The core effectiveness of this is that it lets you taunt your opponent without them being able to retaliate. If, after you make an argument and end it with a statement like that, they try to combat your metadebating by arguing that they're not doing a poor job or that their argument wasn't fallacious, then first of all they don't have any ammunition because the ball is in their court, and second, even if they do, you can call them out for simply claiming their argument is good in the face of criticism without actually defending it, and you'll be technically right. Being put in a one-sided position like this is bound to make anyone's blood boil. It's especially nasty in verbal debates, where not only are people more vulnerable to emotional manipulation, but it also takes up time and space in your opponent's mind, making it artificially harder for them to represent their own argument.
Refer to the opponent in 3rd person. For example, back when I played Spellweaver, I posted a thread on the forum about cards I thought were overpowered, and one of the responses was verbatim, "None of the cards the OP mentioned are particularly overpowered". The core insult here is the implication that my beliefs are so crazy I'm not even worth trying to reason with, and so the asshole turned to the rest of my audience and focused on convincing them instead. It's made stronger by the fact that he didn't even pretend to counter any of my points. If memory serves that was literally his entire post (there might have been one more similar sentence or something).
Now, one thing needs to be said: some people aren't worth trying to reason with. Most people, in fact (at least on some issues). In particular when it comes to politics or religion, most people these days care so much about the sense of identity they get from the group they're part of that they're simply not willing to change their beliefs no matter what argument you give them. When I argue with my parents about Anarchism their argument is different every time and half the time, the conversation ends with them acknowledging "that's a good point", or something, and then the next day they've completely forgotten about it. But good and earnest people obviously hate to be seen this way, so having their opponent refuse to speak directly to them is very insulting to them.
Laugh. Showing some amusement at your opponent's arguments is the most condescending way of taunting them. It's because you wouldn't laugh at just any bad argument, you'd laugh at an argument so bad that you at first wonder if your opponent is serious, or that you feel bad for anyone stupid enough to honestly believe that. Used well, "lol" can be one of the most inflammatory words in the English language.
Put words in your opponent's mouth, aka the strawman fallacy. While many logical fallacies are dangerous because a well-versed opponent can handily call them out and make you look like a fool, the strawman has a special place as probably the best one. It has the following advantages:
Low punishability, since you can just claim you genuinely misunderstood the opponent's argument and that it's their fault for presenting it poorly (extra insult factor as you fork them with the choice to either let your bullshit stand and cut back to the argument or spend more time on something that isn't the point - perhaps leaving you the opportunity to accuse them of sidetracking the debate).
Good audience-convincing power - if someone is just scrolling past and only thoroughly reads your argument, you have very high odds of winning that person's upvote. Even if someone did thoroughly read both sides, when they see your accusation they're likely to wonder if that is what your opponent meant and they're the one who misunderstood.
Highly inflammatory. No one likes being slandered, especially if the debate was already heated.
In particular, it's often useful to accuse the opponent of flaming you. Since everyone looks down on flaming so much, even much more than they should, and it also doubles as a sort of ad-hominem - while making it look like they're commiting an ad hominem. Nasty.
Comment on the opponent's tone or emotional state. Telling your opponent that they sound angry and they should calm down or similar is a commonly employed technique. A self-respecting person doesn't want the help of someone they're mad at managing their emotions during the argument with them. Such an idea is incredibly insulting. This technique makes you appear like you're being nice and trying to defuse volatility, but of course if you were actually trying to do that, you wouldn't be acting so patronizing.
Sore winning. God, how I hate this one. Sore losing is mostly harmless because it's done from a low-status position and so it can't really hurt anyone, it's just a desperate and pathetic way of hiding one's embarrassment. But sore winning is orders of magnitude more powerful and evil, because it's used not to protect oneself but to leverage an amoral victory to hurt the feelings of someone whose feelings are likely already hurt. This shows up in argument after winning a point by insulting your opponent's intelligence for holding a false belief.
One of the last arguments I had before more or less leaving the Prismata community was an example. Another player and I disagreed on whether a position was winning or losing for player 2, and the argument stayed completely civil right up to the point where he convinced me and then he said, "0 isn't 2 so that shouldn't be a confusing thing". Naturally, since this was when my understanding of the concept of inflammation was still nascent, I responded by righteously calling him an asshole and the least qualified member of the moderator team. I actually realized what had happened an hour later and went back and edited the post to instead say "lol you sure like being rude". This way, he doesn't get the pleasure of seeing me upset or the potential excuse to remove my post. I never saw how it went down, because I disabled inbox replies.
The only downside of sore winning as a strategic technique (besides the fact that you first have to win in some capacity for it to be effective) is that it's the most likely to be considered uncivil by observers. But if it succeds in getting the opponent to flame you (which it's incredibly good at), then that almost certainly makes up for it.
There are probably more techniques out there, but for now, these were the ones I could put my finger on. I hope that I've given you a clearer understanding of how inflammation works so that you can more easily notice your opponents doing it and hopefully resist the urge to flame them.