I have the same issue, though at least when the spam is deleted from the Replies admin page the “last author” is updated to a valid user.
Is there already a bug filed for this somewhere? I’d like to contribute a fix if I’m able to.
Sounds like a bug. Please make a ticket, and a patch would be awesome. Probably just don’t run the forum update handler if the post status is not published.
Bug created at https://bbpress.trac.wordpress.org/ticket/1631 with screen shots … apologies for switching WP accounts on everybody. I’ll start looking into this and submit a patch for review when I can!
