> Sites like reddit and HN also allow edits in certain contexts/timeperiods

On Reddit and HN it is also commonly considered etiquette to have append-only comments, writing "EDIT:" in front of the addition to make it clear to readers what is going on. Moreover, reddit indicates in the GUI that a comment has been edited, unless you do it very quickly. Kind of like a git commit, changing a comment that people have already read is considered undesirable.

Reddit also stopped allowing edits of post titles, because it was subject to too much abuse. Twitter is going to face similar problems.