This is definitely an interesting discussion to read. Everything was pretty cut and dry on appropriate moderating until money got involved. Almost everyone agrees that profanity, rudeness, and ad hominem attacks are inappropriate.
This affiliate link business, though, is pretty murky. It seems definitely appropriate to comment on a post on someone else's as a way of simultaneously contributing and promoting your site. I have to say, adding an affiliate link directly to someone else's site seems to be inappropriate to me.