One person did point out that it is just a game, yes but that doesn't take away facts of how it is rude, all in my opinion of course. I think it is wrong and egotistical but however, I need to get over it because people are going to do it regardless if I don't like it and there's nothing I can do about it nor do I want to do anything about it. Just all the more reason to beat their ass.
If by overkill you mean continuing a regular combo then I actually don't mind that. At all especially if someone is practicing with a character and needs to get those combos memorized.