Again, your desires and expectations don't fit in to Brian's responsibilities other than for him to take yours, mine, and 20,000 other viewpoints, and distill them into a sensible set of ideas and communicate those to the company. THAT'S IT!
Unless, he is somehow contractually prohibited or required to post here or elsewhere, then his rights and responsibilities in that regard are absolutely no different than yours or mine, IMO. You don't post everyday, everyweek, etc. Nor do I. Whether he wanted to or not, or did or didn't, is completely up to him and he has every right to do as he pleases if you ask me. If you want to disagree with the content of what he posted, do that, but to complain or object to his posting frequency, while your right, has nothing to do with his responsiblities as Shareholder Representative to the Advisory Board, and that's where all of this thread started, with people expecting something of him that was not his responsibility/role.