Thank you both for clearing the terms of reference, that was helpful. I agree there's an edit window for second thoughts and it might be ten minutes, I've been known to set it as a day. You're left with a thread that can't change at the whim of a user, which is necessary if the author decides to want to look good a week later with an update.
Dealing months after the event with an irate threat of litigation is something any forum might be faced with, and doing the least amount of harm is balanced against the legislative framework. In practice the requirement is uncontentious.
The far side is when someone demands the removal of all their posts, at which I draw the line and there's no legal necessity. Twice I've been faced with an irate demand from a moderator with sufficient access rights to do it themself, and that's down to bad admin in my opinion when they go ahead before slamming the door. There is, as best I can see, no legal right to be forgotten any longer in a European/UK setting - the right of erasure extends to personal information and no further. And in the States, presumably, it's still the Wild West and a bonanza for lawyers.