Having said all of that, I wonder if Ande's idea isn't the best (regardless of what format you choose to go with for the blog). If it was still public with no comments, but you cross-posted entries in a private forum, you could allow people to respond and discuss in a controlled/private environment, but still keep the blog itself public. I'm not sure how much extra work that would be for you, but if it was negligible I would say that's the best option for running your site the way you have and seem to love, but keeping the riffraff at bay.