Hi there,
I won't try to hide my prejudice: I like organizations with a liberal comments policy. If you've spent much time on TechSoup's forums, you've come across criticisms of TechSoup. I think that openness combined with expert leadership is a great formula.
I wrote a blog post awhile ago about the Air Force's social media strategy. This was mainly about discussion on non-Air-Force-controlled sites, but I think that their system could be applied to moderating comments on your own pages as well. The Air Force uses a simple flow chart that distinguishes trolls from legitimate complaints, and I think that understanding that distinction is essential to a good moderation policy. Don't waste your time engaging in an argument with people who are just trying to be annoying, and don't insult the intelligence of people with legitimate criticisms (even if those criticisms may be incorrect).
Cheers,
Elliot