However, I don't know if anyone else shares my impression about OB commenter quality, so I may be completely misguided here.

Absolutely. OB posts are worth a read occasionally but the comments are not. And here I include even comments (not posts) by Robin himself. The way Robin replies does, I suggest, contribute to who is willing or interested in commenting there. Status interferes rather drastically with the ability of prominent figures to engage usefully in a public forum. By public forum I refer to the generic meaning not electronic adoption. It is often the case that hecklers wishing to shame and express outrage are the only ones who consider it worthwhile to show up.

For my part if I was particularly keen on discussing a topic from OB I would consider bringing it up on the open thread on LW.