Well, one way to identify a troll or trouble-maker is with the Report Bad Post function. I've seen a few messages in my online history from admins pleading with people to USE the feature, maybe because they don't have the time to sift through each and every post. If an admin is identifying a troll, my assumption is that they would take a look at the context and judge accordingly.
And if you want to compliment a good post, there's the handy Quote button on the bottom. Just say "Good post! It was helpful because...". That's the way it's been done for a long time, and it's worked fine. Plus, it is a more visible and open form of a compliment anyway.
I dunno, not a big deal.