When unwelcome trolls visit your weblogs and treat you like a dog, it reminds me of that most basic of animal instincts: Marking the territory. They think their scent trail confers a right to stake a claim.
As stray dogs spray shrubbery, stray trolls drop unwelcome messages. Their purpose is to relieve themselves - its not your lap or leg they want - and responding to them only encourages them. Never cave to temptation by starting a conversation. To rid yourself of nettlesome pests, does it make sense to reward them with a bone?
Cayenne pepper or Dog-B-Gone may work outdoors, but repellants have no effect on the Internet. I recommend a liberal use of the ‘delete button.’ Even the most persistent critter responds to Pavlov conditioning, gets the hint, and eventually goes away.
Which is more important to you: The quality of your online interactions, or counting the number of snarls and yelps in the Community Dog Bark of your comment box? Once you rid yourself of annoying pests, think of the free time you will have to read a book, write the Great American Post, and keep in touch with exalted loved ones.
Update (Sun Apr 10, 2011): For more commentary on this bane of bloggers, please go to Bloggingdino's classic post, You Might Be a Troll If ... (A Long Essay on Trolls and Trollery).