I think you'll find that Karma is forum-centric, not site.
If a site has the forum section in which Karma is given....then it will be visible/counted in that site.
Almost but not quite. Karma is primarily site specific. In other words when on any one site you will *initially* only see the karma given from that one site.
So if you've only received karma from one site that is the only site you will have non-zero karma on.
Now once you have received karma from more than one site is when it gets to be more forum specific than site specific. Once you have received karma on a second site *and* assuming that the two sites in question share the same forum only then will you see karma received from both sites and only from forums shared by both sites.
Basically you need to receive karma from a site and that will then "enable" your karma to be seen on that site. Of course what will be seen is only karma from forums that are shared between those two sites but until you receive at least one ponit of karma from another site you won't see any karma on that site even though you may in fact have received karma in a forum that is shared by that site.
I know this is complicated so here's an example. Let's say I have 100 karma but it was all received from the GalCiv2 site. Therefore on the GalCiv2 site I have 100 karma but on stardock's 11 other forum sites I have no karma. Now let's say that my karma consists of 50 points given in threads in the Off-topic forum (from the GalCiv2 site) plus another 50 points given in forums that are only on the galciv2 site.
Now let's say someone on JoeUser gives me a single point of karma. First off that enables my karma on JU and secondly now any karma that I've received from *any* site as long as it's from a forum that is visible on the JU site will suddenly be visible. So assuming that the Off-topic forum is the only forum that the JU and GalCiv2 sites have in common then suddenly it will appear that I have 51 karma on JU and 101 karma on GalCiv2.
Note however if I am on the JU site and I examine my karma it will say that I received 51 points from how many people have given me karma visible in JU forums from *all* sites but it will only list the 1 point received on JU.
So basically once you've received karma from a number of sites it can get difficult to find out who gave you new karma. You really have to "scan" through all of SD's forum sites to see who most recently gave you karma.
Just examine the karma on your "main" site. For me that's
Then scan though the other likely sites from which you may have received it.
And etc. until you find who gave you the recent karma. That's really the only way to find out for sure.
Besides the above listed three site the other possibilities are the following.
Although the two themes sites and the political machine site have very little traffic these days. There's also a TGN forums site but the url format is somewhat different and that's probaly not much used anymore either.
As far as how much karma one can give that's dependent upon your forum rank on a particular site which is not much used anymore except perhaps wincustomize. On GalCiv2 I can give 4 karma whereas anywhere esle I can give only one. However you can view threads in forums that don't even exist on your site by accessing the thread directly.
For example http://forums.galciv2.com/364993 is a thread that exists in the Metaverse forum that only exists on the Galciv2 site. However this thread can be viewed on any site simply by using the http://forums.stardock.com/364993 syntax. So if you have an elevated rank on one site you can give karma from that specific site. If you really want then you can also go to other sites giving the 1 point of karma from different sites to pad the total as well as enable someone's karma from multiple sites. I actually often do this and I just take care to use the same comment for the karma from different sites. That way it's more likely that someone will see that you're the one that most recently gave them karma although it probably will be tough to figure out precisely how much they gave if they do this.
BTW all stardockians give 9 points of karma by default and very few "normal" people except for WC regulars have elevated forum rank.
Now you know all there is to know about how karma works.