>I don't know if it's safe to assume longer tenured members inherently have more class when offering feedback.

I don't think it is. If anything, tenured members may feel more entitled to be rude without consequences. Karma isn't really a measure of civility so much as popularity over time, and it doesn't really communicate any context. Also, if there were a minimum for commenting, there should be a minimum for posting, which might leave new users with interesting projects out.