Can someone define "concern troll" for me?

[Elusis]

@FoolishOwl

Concern driving trollies is a particular form of driving trollies, in which someone brings up something, claiming it’s a tangentially related issue, in order to draw the participants away from the original subject of discussion. It’s often entirely reasonable to bring up a tangential issue and insist on its importance, so this form of driving trollies is a subtle one; we have to distinguish between an honest and a dishonest intervention in a discussion, based upon our belief about the intent of the person intervening. The key thing is, the concern trolley doesn’t actually care about the tangential issue they’re bringing up, and may reveal themselves through this.

“OMG your health, you’re going to die, you’re never going to see your kids grow up, you’re costing the rest of us money, you’re giving people permission to be 700 pounds” etc. concern driving trollies any time a fat person dares to be fat in public and not apologize for it - fails to meet this definition, but is most definitely concern driving trollies.