Also if you search the forum there has been several posts in the last month alone about the reputation system.
You can also go to your USER CP and see the comments left and sometimes they might put their name beside the comments, otherwise it is optional
I found some info for those curious:
The tooltip text changes for certain levels of points. The list of these points and the accompanying tooltip text is below:
<-50 = [User] is infamous around these parts
-050 = [User] can only hope to improve
-010 = [User] has a little shameless behaviour in the past
0000 = [User] is an unknown quantity at this point
0010 = [User] is on a distinguished road
0050 = [User] will become famous soon enough
0100 = [User] has a spectacular aura about
0200 = [User] is a jewel in the rough
0400 = [User] is a glorious beacon of light
0700 = [User] is a splendid one to behold
1000 = [User] is a name known to all
1500 = [User] has much to be proud of
2000 = [User] has a brilliant future
3000 = [User] has a reputation beyond repute
Why do some member's reps count for more points than others?
The amount of points that you give or take from a member's reputation count is determined by your reputation "power". By default the power is 1, however, you receive one extra point of reputation power
* per 1,000 positive reputation points received,
* per 4,000 counted posts, and
* per complete year that you have been a member of the Forums.
I tried to rate someone and it said "You must spread some reputation around before giving it to xxxx again".
There is what is known as a reputation "spread" in effect. This is a minimum number of members you must give reputation to before you may rate the same member again. At the time of writing this number is 6.
You will also receive an error if you try to rate more than 6 members within a 24 hour period