@taste Did you start your forum up again?
Edit: I restarted it for you 😄
I was browsing webmaster tools and discovered that URLs in the sitemap are not the canonical URLs. This seems to cause confusion with the Google Indexer and for SEO purposes confusing the indexer is not a good idea:
This is causing a 404 on maybe the most important page in the sitemap. Granted
/forums/ is probably getting indexed no matter what but errors are errors and they're always bad for SEO.
Same image as above. The content on the categories page can change on a daily basis. Why is it set to weekly? Groups on the other hand rarely change.
Regarding the duplicate/canonical URL issue. I'm really not sure what the right answer is. Maybe it's fine the way it is, maybe the canonical URL should be the expanded version (then the sitemap might change a lot causing other SEO issues). I just wanted to bring it up for discussion.