You can click their user name and see (in their profile) if they allow IM or email, then contact them that way.
You CANNOT post a question saying "User, I need to talk to you."
Responding to their answer by editing your question is considered chat, unless it adds needed details to the question.
CHAT: Nancy, you are correct, thanks.
CHAT: Nancy, you need to re-read the question, that is not what I asked
OK: To clarify, I was asking about the 1972 World Series, not 1927, and the Boston Red Sox, not the Chicago White Sox.