It used to be that if people "thumbed up" your comment, you earned points. Later, that seemed to stop working.
But there's another reason for doing it: For someone who doesn't have the time to read ALL the answers to another person's question (I consider that the original questioner is morally obligated to read all the answers that others have taken the time and energy to formulate, often with a great deal of thought and care), the NUMBER of "thumbs up" on a particular comment SHOULD indicate just how useful it is.
I have seen loads of EXCELLENT comments without a single "thumbs up" - even though the questioner has written "Thanks so much for your advice"!!!
Come on, People! This site should be used for mutual support. You shouldn't "thumbs up" every comment you read, but how much energy does it take to do so to a comment that you find REALLY useful???
p.s. The same goes for shared work: If I haven't got time to read 3 long pieces, it would be nice to be able to see at a glance just how well-received they've been by others on this site.
I will 'thumbs up' if I like the comment. I haven't yet chosen to 'thumbs down' if I dislike the comment. It's in my nature to remain zipped rather than get negative. I read all the questions and all the comments. I rarely comment on a shared work.
I have rarely give a post the thumbs-down, but I often give replies to questions the thumbs-up. I hope that by doing so, I encourage people to reply to more questions and keep the forums active.
I agree, Jimmy - if someone likes my comments, but doesn't say so, how do I know? I'm not sure people read them all, which is their choice, but it would be good if, when they did, they let me know by thumbing up or down - whichever applies.
I don't do this for the points - I do it because it's what I do, and it takes a lot of time; so if you like/dislike what I write, please spare a thumb!