Gina Trapani at Lifehacker has a pretty good guide to making comments on weblogs - from what I've seen, there are a lot of folks out there who could benefit from reading it (not you, of course, but you may know someone who could use it). If you're too busy to read it, here's the "Cliff Notes" version:
- Stay on topic
- Add something to the discussion
- Don't comment just to make a comment
- Know when to comment, and when to email
- Don't be a know-it-all
- Make the tone of your message clear
- Own your comment
- Be succinct
- Cite your sources
- Be courteous
- Don't post when you're angry, upset, drunk, or emotional
- Do NOT feed or bait the trolls
There's much more there - click
here for the whole thing.