An excellent reminder,
Mithalwen, and good points, especially those added by
Bęthberry and
alatar. Yes, positive feedback is encouraging, and I think it is important to give newcomers and shy posters that kind of reassurance. The community aspect is certainly an important one. I know that it makes my day (and I'm no newbie around here, nor am I shy!) when someone gives me a positive comment after I've made an effort to post well.
Look closely at the words in the box when you click on the rep icon:
Not, "I agree" or "I disagree"!
I can recall giving a positive rep and comment (signed, of course) to someone with whose posted opinion I did not agree, but it was stated so thoughtfully that I thought it deserved to be rated positively for that reason.
I have also given a negative rep with comment (signed as well) to a post with which I basically agreed, but it was stated so aggressively that I did not approve of the manner of posting.
Yes, I do give negative reps, but only when I feel that the poster has expressed his/her opinion in an inappropriate manner, or when the same opinion has been stated so repetitively that it is exceedingly boring. However, most members here on the Downs post enjoyably, so the positive reps I give are certainly in the majority!