> Time spent participating online is time not spent honing your craft, and so there should be a strong inverse correlation between posting frequency and expertise.

I disagree. Many people (including myself) have observed that qui docet discit, and there is little better way to teach yourself than to discuss and debate and work with other people. This eliminates your claimed strong inverse correlation, and the rest of your suggestions simply become ways of finding additional information and not corrections for any systematic bias in available experts.