I don't follow OB, but your comment sent me over there to look around. What I saw was a lot of criticism from feminists regarding posts by Robin that had a strong anti-feminist odor to them. I also saw some posts on less controversial subjects that drew almost no comments at all. So the natural presumption is that those feminist commentors are not regulars, but rather were attracted to OB when a post relevant to their core interests got syndicated somewhere. If that is what you are talking about then ...

Well, sure, a registration system might have repelled some of the commentors. If Robin really wants to insulate himself from feedback in this way, it might work. But I rather doubt that he is the kind of person to exclaim "OMG, we have wymin commenting here! Who let them in?". I hope his regulars aren't either.

Some comments on topics like this are emotive. Admittedly, you can't really engage with them. But that doesn't mean you shouldn't at least read them, count them, and try to learn something from their sheer existence, if not from their logic.