Here's mine: comment/text post preview (because why not?)
Do you mean that as I am typing this comment I might press a preview button to show me this text that is already right here in this text input?..
I don't mean to pick on the asker, but why is it that these days so many people posting to Ask HN just write a few words and then expect everyone to fully understand what they mean?!
Long story short, HN is run by two people whose ethos is "change as little as possible", because they think that's the best way to keep it alive and a force for good. I would kill for the opportunity to help them out with small stuff like this and my personal hill-to-die-on--more markup than code blocks and italics--but I wouldn't hold your breath.
They've got their gameplan and they're sticking to it, and you kinda can't help but be impressed by such an honest centering of ethics in their work. Certainly not something you can find on the two other options, Lemmy and Reddit; one is kept busy trying to keep things democratic, and the other is 100% focused on adspend and CostPerClick post-IPO. Despite my disagreements, I'm damn grateful that they exist!
I always felt it helped keep some people from posting throwaway comments.