I noticed something really strange with google serps for some of my pages; when searching for the exact title of the page (tried in quotes and not in quotes), it doesn't come up in results, but sites that have copied my content do. Furthermore the url from my RSS feed sometimes appears instead (which redirects to the page in question)
If I do a good old site:url.com the page is in the index.
If it makes a difference the site is a large forum that is 10+ years old.
It sounds like you have lost authorship or authority for this bit of content. If authorship markup is not practical (and I realized it may not be practical for a forum) you might read up on pubsubhubbub. This is especially so since it seems your RSS feed is part of the problem.
Thanks for the reply. I actually have authorship markup on the thread pages. I don't see the problem where an author, like myself, is linked to my Google account.
The problem seems to be occurring on thin(er) content thread pages that previously were appearing on serps. I can't figure out why they were dropped. It makes no sense that sites that have then copied that same content are coming up in results instead.
I have since done a small redesign and cleaned up a lot of erroneous code - mainly extra css and unnecessary js menus - but that hasn't helped.
One thing I did just realize is that the one site copying my content is also pushing to friendfeed. Interesting. I'll have to look more into pubsubhubbub.