Courtesy stamp

Namely don't post rude comments on peoples pages and if yo have a mature contented image please put it under mature content because little kids look at this website as well.
Also not everyone is a great artist so don't tell them their art sucks just to be a smart aleck. Everyone has their own style. Learn to appreciate it and if you don't like it. DON'T leave a comment unless you're trying to help them get better.

BTW telling somebody to "GTFO" or "OMFGYOU'REARTSUCKERS!" is not constructive critisism.