It's very common that other users comment and suggest ways to improve your answer. In almost all such cases, the user gets credited in the answer ("Saved 6 bytes thanks to ... ").
A lot of those comments are removed by the user, while many are kept, at least for a while.
Is it OK / a good thing to flag such comments as obsolete, if proper credit is given? I've done this a few times on other people's answers, (and the flags are always accepted), but I sometimes want to do this on my own answers as well. I'm not sure if that is considered rude, or if it's a good thing to clean up the comment sections.