I think it’s important to use grammar correctly. I believe that people would always prefer to do any endeavor correctly, no matter what the activity. If you think it is uncivilized to correct misused English, that’s fine.
It’s certainly rude to do it so quickly and not even be correct - completely unnecessary.
Comments are not essays. I’ve many aspects of my life that need full attention, having 100% correct English isn’t one of them. I’m hardly terrible either.