This is a sticky issue for sure. I'm not sure how many libraries have thought through this aspect of diving into the blogosphere. In a quick search, I only found one example of an online library blog policy:
St. Petersburg College Library Blog Policy.
And there's the
LITA blog policy].
I found some interesting reflections on the problem. They're not specifically from the library world, but the points made are quite relevant. In
Crafting the Ideal Business Blog Comment Strategy, the author states that "if a blog has a recognizable business sponsor or individual shepherd, then everything on the blog has an implied ownership, a brand identity, of that owner."
In
Can Bloggers Be Sued Over Comments? Maybe, this statement got my attention:
"If you moderate or edit comments to your blog in any way you're probably assuming legal liability for the content of those comments."
The author issues the caveat that this is in no way official legal advice.
I hope that those libraries that have taken the plunge into blogs with public comments will share their experiences and policies.
Or you can craft one and share it with us, librarybob! You have been the source of so many good ideas here.