To be clear, someone at Trust Level 3/Regular can’t edit content of posts, just the title of a topic (eg for this topic “What additional privileges (if any) does Regular status in this forum actually provide?”) or move a topic from one category to another (eg from General to Bug Reports). That’s it.
@bouteloua is a moderator, and moderators can edit the content of posts, but that’s generally only happened a handful of times, and those edits should be free for anyone to see. The original poster is also notified when this happens. I think it’s pretty much only been done to fix links and such.