I disagree with the idea that they can or should be forbidden outright.
I gave up on a outright banning long ago. Simply having some separation by not listing the Off Topic forum in the recent posts list is probably the best idea.
In a similar vein I would also prefer more separation between the different stardock sites. I personally have no desire to see any of the windowblinds/object desktop, sins, political machine, etc. threads.
It seems the kinds of folks that inhabit these different sites have different interests and perspectives that make interaction between them somewhat problematic. I really would prefer a GalCiv2 exclusive site and let everyone else have their exclusive sites as well. If someone does actually have interests in multiple sites then let them go to the different sites or to the catch all forums.stardock.com site.
Making forums.stardock.com the common site allowing access to all sites and then limiting forums.galciv2.com, forums.sinsofasolarempire.com, forums.politicalmachine.com, etc. to their respective dedicated threads makes a *lot* of sense.
I specifically come to forums.galciv2.com as opposed to forums.stardock.com. By doing so it seems to me to imply that my interest is limited to GalCiv2 as opposed to Stardock's entire offering. Why must I be forced to wade through a multitude of threads that have no interest to me.
I do realize that there are some topics (such as Impulse) that necessarily span multiple forums but even so I believe such things should be kept to a minimum. Frankly these days I probably have interest in far less than one in ten threads that I see on forums.galciv2.com.
There's plenty of people on here that type quality stuff who have 0 karma. Likewise, there's plenty of people with many karma points whom, in my opinion, are somewhere out there in space with their ideas and opinions.
Per the above comments note that karma is separate dependent on the site from which it was given. Take a look at Frogboy's post in each of the following three forums. In each case different karma is reported.forums.stardock.comforums.sinsofasolarempire.comforums.galciv2.com
Also take a look at Kitkun who has 0 karma in forums.galciv2.com but 38 karma in forums.sinsofasolarempire.com and 37 in forums.stardock.com whereas I have 0 karma at forums.stardock.com, 5 karma at forums.sinsofasolarempire.com and 38 karma "here" at forums.galciv2.com.
The more I think about it the more sense it makes to have forums.stardock.com to be the central location for *all* forums and then allow the individual forums to be more restrictive to content dedicated to each individula site's purpose.