Based on my experience I think that if your comment has actual value to someone (for example useful/helpful in some way) they will probably upvote your comment.
You could also get upvotes If your comment is relevant to the post and/or funny.
However I received a lot of spam-like comments lately and I'm simply just ignore the one-two word spammer comments.
People who comment things like "nice post" are spammers and they are just showing how ignorant they are.
They doesn't really care about your content. They just wants attention for their own good.