The exact mechanics have changed over time so I'm not certain what they are at the moment. A very simplified explanation is that your rating is an average of those up and down arrows you see. Any poster with pretty much a decent or higher rating may rate your posts.
Late to the show, but just so you know... also, Kao can delete this if it's some kind of SUPAR SECREET information. I sorta doubt it, as we old-timers all knew of it back before the changes.
Numerical explanation - you have an overall karma score. The starting score is 3.00. Every time you post, your post is rated at that score twice. When you are rated up (6.00) or down (1.00) the scores are all averaged. So if you had a 3.00 score, and posted, it reads as
And then that gets modified by ratings. So,
would give that particular post a karma of 4.00. Your own karma on future posts will also be increased.
You get titles based on your overall karma; none for 2.00 to 2.99, Scholar for 3.00 to 3.66 (Decent rating), Sage is 3.67 to like... 4.33 (Good rating)? I forget, might be 4.66. Guru is above that (Excellent rating). And then there are custom titles given out for folks with way too many posts (10k+, usually).
IIRC, these numbers were all made invisible several years ago due to drama. They're still there, but you can't see them. Also, a Nuke is -15.00 (but I don't think it affects your overall karma), a ban is -50.00 and sets your karma to that, and Admin status is 5.00. Unless you're Kao, then you have an innate 5.03
If you lose Admin status, you go back to whatever your posting karma was prior to that - not sure if all those 5.00 posts made as an admin count in the overall karma. I hope so
Edit: And yes, nobody really cares about Karma. Making the numbers invisible probably did help a lot. Edited, May 17th 2013 1:49pm by LockeColeMA