The {actor} is still showing up on Joomla 25 with jomsocial 31 using

Correct. We can't fix the old ones, as that's simply how JomSocial works. There is a MySQL query that we can provide that will strip it from all old posts, if you're interested in that.

The next release of the JomSocial profile plugin will also have the "xyz just posted new Facebook status" (or whatever the string is) in a language file so that it can be easily translated. That will work on previous status updates, just so you know.

Thanks,
Alex