Many other boards have an edit button that only allows edits for five minutes, and even then adds that it has been edited. Yes, someone could post a 'nasty' comment and delete it 4 minutes later, but it's clear that the post has been changed, and the odds are that not everyone has read it.
IME that sometimes leads to people posting screenshots of the original, but that's usually just to put paid to false accusations of tactical editing.
On the whole, an edit function stops all the 'I meant to say bilge instead of bulge' posts - which can be useful, but cuts down on the comedy opportunities 