The idea seems to be common that there's a "second level" of giving your word: a promise. According to promise ideology, a promise is "more severe" or "more trustworthy" than ordinary word, and breaking one is worse than going back on your ordinary word.

The most imminent problem with promise ideology is that it depends on language details. In morality, if you voluntarily do something that causes someone else to believe something, that's giving your word - no linguistic implementation details involved. The only concepts needed are universal ones. But for promises, it's not clear how that would translate to a language without a word for it. How could you express that concept? If the concept of a promise can only work with a language that explicitly supports it, then it's not a good concept.

Here's another problem with promise ideology: if you give your word, and someone asks you if you promise, you're forced to either promise or refuse to promise which of course indicates you're lying. Which means to be convincing any lie would have to be a promise and anyone would make you promise if they really needed your information to be true. Promises just replace "basic" agreements if you care enough.

The only reason this doesn't get exploited in practice is solely because people are effectively prohibited from asking you to elevate it to a promise, as that would suggest they suspect you of lying which is socially looked down to a totally irrational extent. So basically believing in promises turns honesty into a degenerate game of reputation and unspoken distrust.

I only use the word "promise" in reference to a past declaration made to reflect that other people might be counting on it. I might say, "I promised to release RTTP this week, so I have to get it done", but I'd never say, "I promise I'll get it done", because that's strictly redundant over "I'll get it done". (Unless I'm trying to deliberately exploit this concept to increase my chances of deceiving someone, which I obviously would do for a greater good result.)