Since karma is not a merit and is not used to rank up, they way I give it completely depends from my mood. If I see good posts, they I definitely give +karma. It is not like I evaluate post from «if it gives valuable information», but for me it is enough for post to be well written and contain new idea (for example I would not give karma for post with «DYOR is a must», «not your key=not your crypto». That is basics that everyone knows and repeat each day on the forum). And I dont remember giving someone negative karma. If a post is bad, spam, useless, contains bad words, offend someone - I simply ignore it like it does not exist.