Should I delete my comment after OP fixes/golfs OP's code?

I usually comment under an answer if I've found a mistake in the answerer's code. I also do it when the code can be golfed more.

After the answerer fixes/golfs his/her code, should I delete my comment?

Also, if the answerer has comment something like Thanks! replied to my comment, should I flag it as obsolete/not-constructive or something else after I've deleted my comment?