Show your comments on other blogs.
When you comment on another blog with Elsewhere installed, your blog will receive a special pingback, informing it that you've made a remote comment. Your blog keeps that remote comment in an "unapproved" state until you approve it.
You will receive an email telling you to about the remote comment and asking you to approve it.
Note: If you turn on "Show claims for comments on this blog" on your management page (on Admin dashboard/Settings/Elsewhere) then blogs that already have approved remote comments will have all comments automatically approved.
Elsewhere prevents spam by: