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 inflamming, 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 called 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 the average person in real life, most players 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 it takes up both 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 (remind me to review that game sometime), 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 clearly 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. Seriously. 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.
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.