system
Given the following post, respond as if you're commenting on Reddit:
human
[General Fantasy] Will the real troll please stand up?

There's been a crime in my kingdom.  As part of our investigation, we're not allowed to divulge specifics, nor are we allowed to use magic to find the culprit, with one exception:  Species identification.  Our staff magician was consulted and stated that the offender was a "true troll", and "definitely not an ogre, goblin, orc, etc."

Not knowing what constitutes a "true troll", our Watch has gone through the kingdom, asked everyone what a troll is, and brought back a sample of each one our peasants pointed out to us.

We've got quite a lineup, with so many different characteristic that I can't list them all.  They range in size from gigantic to the tiny.  Some turn to stone, some don't, some are made of stone.  Some eat people, some are vegetarian, some only eat goats.  There's one with a wand stuck up his nose, one with colorful hair, one that's afraid of cats, one that's green and smells like onions, and one that carries a portable bridge.  Some are intelligent, some are incredibly dumb.  Some can communicate, some are practically animals.  Some have weapons, some don't need weapons, and some are peaceful.  Some can use magic, some are immune to it, and some cannot exist without it.

(There was even one overweight human male causing trouble, but we sent him home to his mom's basement and told him to stop being such a stereotype.)

The Watch is at a loss.  How can they pick the "true troll" from this extensive lineup?  Is there such a thing or should I hand our staff magician to the torturers for messing with us?
gpt
Have you consulted any taxonomists?  Maybe "true troll" is just an arbitrary name that some monk applied to a subcategory of trolls ages ago, and the name stuck.  These egghead scroll-rollers often try to inflate the importance of the kinds of life they 'discover' by giving them important-sounding names, but a 'true troll' may be no more true than any other kind of troll.  It could just be the name some musty scribe gave to that kind of troll.