While you're correct, I think the commenting and voting tendencies of the overall site population tend to drown them out. Intelligent discussions on Reddit seem to have a higher chance of being derailed by e.g. people posting 4chan cliches for cheap laughs.
Of course, he's flattering us, and he got voted way up...
I still think this site has more signal-to-noise than any other social news site except Metafilter, which is a good sign. I can still look at the top stories each day and find perhaps 20-25 that're worth at least a look, and 10 or so that generate discussions that I'm interested in participating in.
Metafilter has a $5 upfront signup fee and diligent moderators. I'm convinced that's ultimately the best way to keep out most trolling and other assorted malarkey.
Of course, he's flattering us, and he got voted way up...