I think that one interpretation of "abusive" posting could be a rapid series of posts that have no substance relating to the subject at hand, but simply comments for/against whatever is going on... maybe even polite, but "useless", nonetheless... more like "abusive" of the time/space taken up without providing anything of value. I don't think Bert needs to cite specific examples. The immediate comments seem to indicate that Bert gave this person more than enough time. I would also agree if Bert even banned this poster, and removed all of his posts, with only a passing "this poster has been banned" note. Being a mod is not an easy job.
Note: I've been a member of a sports team board, which if you can imagine, incites much emotion. The mods there do a very good job of moderating all of the "stuff" going on... and ban posters on occasion. But when banning is done, or posts are deleted, the opinion is one of agreement. In my brief experience, I think Bert reflects that and does a very good job...
