People make mistakes, that's just part of life. 99% of the time I believe there is nothing shady going on. How many other forums are you a member of and how many of them allow you to delete posts?. I'm not mad or anything just saying this isn't SOP as far as forums go.
I am a member of lots of other forums, and there are a couple of social groups I've moderated on other platforms for many years. I try to never delete anything unless it is just totally extremely vile and disgusting. I'd prefer the record of what happened to remain. Otherwise people can easily just erase their mistakes as if they never happened. Then no one learns anything and the same shit continues to happen over and over again.
Sure, people make mistakes. But deleting them prevents others from learning anything from those mistakes.
In fact, I can remember forums that allowed anyone to see older versions of a post before the OP came back and edited it after they'd made the original post, so we could all be aware of what each stage of the post was before each edit by the OP. It kept things transparent, so that nothing removed was ever really lost. I DEFINITELY appreciated that. It was a valuable feature I don't see nearly often enough on online discussion forums these days because once someone edits a post (like we can do here for six hours after the post was originally created), what was previously there is lost forever. I see that as a negative thing.