[pvg]

There's a (small, grey) link that reads 'edit' among the links at the top of each comment you can use if you want to change or add something to a comment you've already written, if you prefer that to replying to yourself.

[randallholmes]

I tried using it, and I could edit, but the update button did nothing; the edit never got posted. So I'll stick with little multiple replies for now.

[pvg]

The edit happens inline, immediately when you hit update - it won’t take you back to the thread but the comment is updated right above the input field (and in thread). It’s not terribly important either way.