Great point. A lot of people debate for debate's sake, because their opinion is out there. That's probably what I do on HN, I post and never look back or respond to any replies. Not a good trait, but anyway.
Best thing to do, if you detect you're about to enter a debate, is to ask "What would it take for you to change your opinion?". If they reply with "nothing" or a vague answer or whatever, exit the debate. Likewise though, ask yourself the same question.
Yeah, couldn't agree more. They also can be annoying online, so people just ignore. On Reddit you often see very long, deep, threads with 1-karma posts that nobody even bothers to vote for. On HN those long debates not only take a lot of space, and you often see moderators telling people to stop.
Sometimes you gotta preemptively "lose" a debate, by not answering at all. At most a "Alright, I get your point but I disagree" which also doesn't really add much to the discussion.
Best thing to do, if you detect you're about to enter a debate, is to ask "What would it take for you to change your opinion?". If they reply with "nothing" or a vague answer or whatever, exit the debate. Likewise though, ask yourself the same question.