It might have been covered but it does seem that google is ignoring iframes in relation to commets code posted on sites.for instance: our text cached version.: http://webcache.googleusercontent.com/search?q=cache:8IZ95GICp7AJ:gaveltek.com/seoblog/&hl=en&gl=us&strip=1
compare the page title to (use headers it easier)
www.gaveltek.com/seoblog the list "comments" and despite there being some the are not posted. However, I do believe general wordpress comments hold some weight. That is not to sayt that facebook comments do not, its just done via different metrics, like social, and trust, and egngagement.
Cheers
TODD
It would certainly not make anyone feel that the product they pay for is only going to be updated if they do it themselves. The double win is super valuable as it clears up the time constraints for you and really steps up a a simple, but valuable product, and updated and frequently.