I used to be active on these forums as a young teenager, and I like my username so I want to keep using it elsewhere, but I don't want to risk people who know me stumbling upon 13-year-old me's angry rants about her parents or ill-advised disclosures of personal information. For this reason, I've been going through my old posts and deleting anything questionable. Unfortunately, the majority of my more sensitive posts have no delete button, presumably because they're in locked threads. Is there a way to fix this? Failing that, is it possible for me to change my username?
On a related note, how do I leave a social group?

I don't know about the deleting stuff, but you can request a name change here

Try asking mods and admins instead: https://modthesims.info/f/24/