The HN community in general is fairly against those sort of comments, preferring instead comments that add to the conversation by either bringing new knowledge or interpreting existing knowledge in a novel way. People are quick to downvote.

The only general solution is to always ask yourself "does this really bring something to the conversation?" before posting.

Also, you shouldn't worry too much about losing karma every once in a while for comments that you do feel are constructive. Karma is meaningless.