WYMHM: "guardians of an emerging behavior code: Twetiquette."

“Some people don’t really understand that it’s just not good Internet etiquette” to type in all capital letters, Mr. Fanaro said.

Yes, he and the other Twitter cops do get quite a backlash, much to their delight. Mr. Fanaro posts a phone number on his Twitter profile page, and his voice mail is full of death threats and foulmouthed rants. For laughs, he sometimes takes his phone to a bar and plays the messages for his friends.

Provoking an irate reaction seems to be largely the point. GrammarCop, one of several people who seem to exist on Twitter solely to copy-edit others, recently received a beatdown from the actress Kirstie Alley, to whom he had recommended the use of a plural verb form instead of a singular. “Are you high?” Ms. Alley wrote back. “You really just linger around waiting for people to use incorrect grammer? you needs a life.” (One of Ms. Alley’s people said that the actress was too busy to comment for this article.)