I usually only -- nodes that are insulting, extremely poorly written, or just a need a push to be reaped (such as a duplicate put up for consideration by its author). If I find what I think is an egregious error in a writeup, I'll post a reply. In the particular case of the node you mention, I didn't downvote it, but I didn't upvote it either. I thought it wasn't terribly informative, and didn't directly address what the questioner was asking. Nonetheless, there's nothing wrong with it; I let it be.

Now that doesn't say anything about how others use their votes. Some are probably new monks who are trying to figure out how the voting system works, and you ended up being part of their learning process. That's part of why I scan Best nodes and Worst nodes, looking for anything that may be getting unfair treatment. IMHO, if you mean to give feedback with a --, a courtesy /msg explaining what you thought was wrong is important. Otherwise people are left wondering.

And if all else fails, just remember the explanation I read in CB a long time ago (forgot the attribution, sorry)

I find some people here are wankers.