Many posts (both questions and answers) on the site have minor/major grammar problems - even in titles. For example "What does ... means?"
Is there anyway to provide a built-in grammar checker on the site?
Answers OnStartups has terrible grammar generally, and Biblical Hermeneutics tends to have wonderfully erudite writing. The difference is in the site membership. Some sites have significantly more second-language users than others. I've seen plenty of bad grammar on this site because users don't have English as a first language, but I've seen very little of the lazy txtspk that we sometimes get on Stack Overflow. That suggests that people are sometimes struggling with the language, but are generally trying their best. The best thing to do is to step in and edit. People who actually are trying their best to communicate will generally welcome edits from fluent speakers.*
I, personally, am a proofreader. That's not my actual job, it's just a facet of my personality which I can't turn off. Misplaced commas grate on me. So when I see errors, I edit. I'm not on this site much, but when I pop by I usually fix up a post or two. If the regular membership do the same, and keep on top of the problem, the quality will stay high. (And the people whose posts are being edited may pick up on some of the corrections and, gradually, start writing in more fluent English in the first place.)
* And let's not mention the time when I angrily rejected edits intended to make a question of mine on Christianity SE more readable. That was ... a long story. I had my reasons, but could have handled it better.