I do read Youtube comments but I agree, the majority of them are just weird, stupid or impossible to understand due to bad grammar. Every once in a while I come across a hilarious one though which makes it kind of worth it xD
i admit it, i sometimes read the comments, and have a good laugh and shake my head and say oh you poor sad fools. people who spend their life making fun of everything they don't like really have issues that tissues can't blow away.
It really depends on the video. If it's a popular video for a latest trend, chances are, the top comments are bad. But if it's a unheard-of or niche video, then the chances of a quality post are much higher.
So really, you can, with quite a lot of certainty, know if the comments are worth reading if you pay attention to what videos you watch on YouTube.