While the improved anti-spam features should help bloggers combat spam, their new “social signal” feature may also help your readers from viewing comments from annoying trolls as well.
The upgraded Comments Box uses social signals to surface the highest quality comments for each user. Comments are ordered to show users the most relevant comments from friends, friends of friends, and the most liked or active discussion threads, while comments marked as spam are hidden from view. [...]
Admins can choose to make the default for new comments entered either “visible to everyone” or “has limited visibility” on the site (i.e., the comment is only visible to the commenter and their friends), to help mitigate irrelevant content. (Facebook Developer Blog)
By only allowing new comers comments to be visible to their circle of friends, Facebook is helping to reduce having a discussion disrupted by a random troll, without alerting them that their comment was censored.
Blogger’s powering their comment section via Facebook can also blacklist words as well as users who are proving to be a nuisance upon multiple posts (i.e. those who spell in ALL CAPS or consistently go off topic).
The only major issues that I have with Facebook comments is the inability to import your comments from Facebook as well as the inability for users to log in with other services (like Google or even Twitter).
For those of you considering installing a third party commenting service, would you consider using Facebook for your readers instead of another service?