If you are having a split configuration where you are hosting the external Community Server site on a different server than the web site that is visible internally but you are sharing the exact same database, or the URL for your blog differs depending if you access it internally or externally, you may find yourself in the situation that Community Server will ping the configured site (or just the links from your post) with the wrong URL. Actually it's not wrong as it is the URL as if you are accessing the site internally, but for all other people outside your firewall this URL doesn't make sense. I have this kind of configuration because I want to post using SSL site, and by default Webhost4life isn't configured for SSL for the subdomains. As a result I found myself in the situation that CS was pinging sites with the administrative URL (SSL), instead of the public URL.
After digging a little bit I didn't found something very relevant and I decided to recompile Community Server to make SiteUrlsData provider aware of absolute URLs. I was ready to send the patch to Community Server team, when while I was browsing for a completely different thing, I found this URL on the Community Server site, that appeared to be linked to my previous needs. So all my patching process was not required at all because the team thought at this kind of need.
So, if you need this kind of configuration do not search further, all you have is to place for the url tag a new attribute named "navigateUrl" with your absolute location and you are done. Apparently, this is not very well documented since even the guy that was asking about the problem found the answer from the CS support. In my case I modified the URL only for "weblogpostId" key, but you may want to modify it for "weblogpostName" too, depending on your configuration.
Also, the good news is that this week it appeared Service Pack 1 for Community Server 2.1, and they are also working hard for the next release that will be named Community Server 3.0. Since 2.0 works good enough for me, I think I'll wait for the later.