An "oops, sorry" would have removed that tag.

A chest thumping "I'll do worse if you don't do what I want" probably won't do much.

And ANY new activity should get a corresponding "unread" mark, no matter how old, regardless of how you think it should work. That was the entire point of adding that feature in the first place...based on the activity of another former member. (assumption being you are deciding to become another former member for whatever reason).