I know how to spot grammar mistakes myself, it's easy, and can always double-check with Grammarly. This is a writing community, grammar errors make it look like crap. If users expect to make money posting, then they should follow the same rules university students do. We dealt with grammar throughout high school and college, you don't make it through unless your grammar is perfect.
As soon as non-English users translate over to English, then they should do their due diligence to make sure the text is coherent. Let's get this clear, I'm not going to flag a user for making a few little silly grammatical errors, but if the whole post is not readable then I may send a flag. There are acceptable grammar mistakes, and then there are the unacceptable ones, and I'm fed up with seeing them in the hive. If a flag can get through to them in the error of their ways, I'm helping them.
As for AI I will use three detectors and if they come up using it over 50%, then it is more than just paraphrasing so quite possible that could be considered ai abuse.