Bryan Henderson—or, as he's known on Wikipedia, Giraffedata—has made more than 47,000 edits to the site since 2007, and almost all of them were to fix one error: the incorrect use of "comprised of." Henderson, a 51-year-old software engineer, is one of the most active editors on the site, and is so well-known that one Wikimedia Foundation employee has called him "one of my favorite Wikipedians of all time." Every Sunday, he runs a software program he wrote himself searching for his pet peeve phrase; any articles he hasn't already edited in the past six months (he doesn't like to annoy overprotective or possessive article editors) get fixed. He usually does about 70 to 80 edits a week, which takes no longer than an hour. "It’s just fun for me," he tells Medium. "I’m not doing it to have any impact on the world."
As for the grammatical error itself, let's just say many people get the verbs "to comprise" and "to compose" confused, and typically, "comprised of" should actually be "composed of," "consists of," or similar. (For a more detailed explanation, see Henderson's 6,000-word Wikipedia entry on the matter.) He puts a lot of thought into his edits, he says, but he's done so many of them that most take just 10 seconds, though some take minutes. Of course, not everyone appreciates his mission: One fellow Wikipedia editor once reverted about 30 of his edits in the same order he'd made them; in 2009, an editor left a comment on the Wikipedia page for founder Jimmy Wales complaining that Henderson "defiantly" continues making his edits "even though numerous editors have objected to his obsessive removal of the gramatically [sic] acceptable term." Wales, however, refused to intervene. Click for the full profile on Medium.