Not sure if you can scan posts that far back, but when I first started here, I was a pretty sarcastic/cynical guy who made a lot of underhanded comments and just went into threads to disagree with or argue with people instead of ever giving any real good feedback on other posters' comments.
Since then, I've become more active (with the exception of the past 2 months or so, since my schedule has been so crazy), and I've been making many more in-depth posts, quality posts, etc. I still have a little bit of my sarcastic tone, which can cause friction in some debates I'll agree (see the Mauer thread- again guys, sorry, I didn't mean to come off as "holier than thou" if I did).
Long story short, since I've become less pessimistic and less of an all-around d-bag, and actually started contributing to these forums in a meaningful way...
1. Long time posters here have PMed me congratulating me on some of my analysis, encouraging me to keep up the good work
2. Mods have PMed me congratulating me on how I dealt with a particularly negative or angry poster in a constructive way
3. Posters from all across the board have PMed me looking for advice and info on their teams, certain players, etc.
What I'm trying to say is that not only does it make the forum better to try to be constructive and positive, it also makes your personal stay here all the more worthwhile.