Quote Originally Posted by Arrowhead
Can everyone stop talking about grammar?
I hate to mention this but I'm not sure the use of a question mark at the end of that sentence is correct.

If the sentence was intended to be a question, (e.g. is it possible for everyone to stop talking about grammar) then the question mark is appropriate.

However, I suspect that in fact your statement was intended to be read as a request, proposal or instruction.

e.g. Would everyone please stop talking about grammar,
or, I suggest that everyone stops talking about grammar,
or, Stop talking about grammar, Now.

In which case the question mark is inappropriate.