English Wikipedia User Xiong coined the Tolkienesque term "orc" to describe a somewhat trollish user with unusual qualities of cleverness, persistence, and flexibility.
Orcs may or may not oppose trolls; they do not troll as intensely as a common troll. An orc masquerades as a genuine user, and may even make an occasional substantial contribution. An orc may fight a troll, or even another orc, hoping to steal the mantle of a knight; but often merely plods along in a groupthink vein, playing to the crowd, gathering support by acting with the mob, and occasionally looking to see where the mob is going -- and getting there first. He hopes to build up a reserve of public trust based on his frequent appearances on the "right" side of battles against straw men. He may thus acquire cat's paws or sparewheels. This is the orc's "passive mode".
When the orc shifts gears into "active mode", he fastens upon some object -- usually another user, but perhaps a group of users or an abstract concept -- and attempts to eradicate him, them, or it. He is unusually persistent and flexible in his attacks. Unlike trolls who generally "ignore all rules" except the most clearly established (since "rules" are so easily manipulated by orcs themselves - see below), the orc treads the edge of the acceptable, attempting to drag his opponent to this unsafe battleground. A successful orc attack is completed when his victim, not the orc, finally crosses the line into sanctionable action (c.f. MeatBall:Sucker Punch and ). But absent this satisfaction, the orc persists until he exceeds community tolerance.
Another feature of the orc is his fascination with policy. He avoids substantive contribution and manipulates policy to his own ends. His flexibility is key. When stymied at one point, he goes to higher ground, looking for some policy that can be creatively twisted to support his vendetta. He fades in and out of active and passive modes, from direct attack to subversion of process. If he perceives a gray area, he pushes it as far as it will go; then he switches sides and pushes there, too, until nothing is left but a fine line between right and wrong.
The real danger of the orc is not that he destroys other users; users can be replaced. It is not that he vandalizes articles, policies, and tools; they can be rebuilt.
The orc, by playing constantly in the gray area between "okay" and "not okay", forces the community to resort ever more frequently to formal procedure, tribunal, and written, explicit policy. That might almost be a Good Thing, but a social group founded on more or less anarchic principles maintains its integrity via meatball:SoftSecurity, which depends on some shared self-image and a certain level of mutual trust. Orderly anarchy, as opposed to chaos, depends on members working to avoid testing limits and provoking contention. By forcing the group, bit by bit, to adopt strict methods to exclude bad actions, the orc destroys orderly anarchy and replaces it with a slapped-together mess of improvisation -- ad-hocracy at its worst - which is easily manipulated by other orcs.
Orcs have a symbiotic relationship with martinets, who strive to create an atmosphere of rules, obediance, and structure as an end in itself. Some manage to be both at once.
The Orc's destruction cannot be reverted. Once that mutual trust is destroyed, there is no way to regain it; once resort to authority replaces shared consensus, it becomes the first resort in all cases. This social glue is precious and fragile, and the orc erodes it by his every act.
Thus the orc is the most dangerous of all troublesome users.