I regularly see people up-vote questions that are about to get closed. Usually the question is an obvious duplicate or a "where to get started" question. I think it's a good idea to try to set the OP straight in the comments and get them pointed to the help they need. Also, if I can see that the OP is really trying to create a good question (albeit off topic) or apologetic about their mistake, I can see not down voting. But wouldn't up voting such a question only give people the wrong idea? Should we discourage people from up voting questions that are "bad"?
Examples:
https://gamedev.stackexchange.com/questions/32589/first-programming-language-c