It would be nice if there were a service where people could write their comments and have them expire after, say 24 hours, but the blogger could run a script which downloads them before that happens. By having a local copy of the comments, the blogger could check them and include the approved ones into their static content.

Each comment would be associated with a salted hash based on either an IP address (for anonymous comments) or an account on a social login provider (like Google or Facebook). By default, a user could only post 1 comment every 24 hours, but the blogger could then publish a whitelist of people who are exempt from that restriction.

If this were an open standard, then the blogger could switch their comment provider at a moment's notice, without losing any data.