Off topic posts annoy me, but I can tolerate them better if the title makes it clear what the post is about. (But I don't like questions marked OT. If you know it's off-topic, but you post anyway you're just bad). If the title is clear, I just skip the thread. If I get drawn (by the misleading subject) into reading the post, I seldomly reply, but I may downvote. And I downvote replies that attempt to answer the question as well - as such replies reward the unwanted behaviour.