I doubt anyone would care about karma, but if you're in the habit of making thoughtful comments, it could help give the interviewer a sense of who you are, the depth of your thinking, the subjects that interest you, your writing skills, etc.

If you were to include your username in the "interests" section of your resume, I think it would do no harm if your comments are reasonable and could possibly help depending on the personality of the person who reads your resume.