In my opinion it’s unreasonable to think anything can truly be deleted in a federated system. Even if the official codebase is updated to do complete deletion & overwrite, it’s impossible to prevent some bad actor from federating in a fork that just ignores deletion requests.
Seems sensible to just not post anything that you don’t want to be available for the lifetime of the internet.
So many, many choices.
I think my all-time dumbest came when I was about 22, so it doesn’t fit here. In my teens…probably driving drunk at speeds up to 100mph on the mountain roads up above Pasadena with the headlights off at night.