Sure! So, a concern-troll is someone who may or may not be an ally, but presents themselves as an ally with “concerns” — polite yet provocative criticisms cloaked in a wrapper of “I’m worried for you.”

They’ll go to great lengths to say “I support you, but I’m not sure you should [do / say / pursue] [X / Y / Z], especially [now / like that / to that person].” (A common example is some variant of “Are you sure want to wear that? I mean … *I* love it, but I worry *other* people might find it too scandalous.” )

More specific to racial justice, MLK’s “Letter from a Birmingham Jail” is a good example of calling out concern-trolling in the 1950s analog world, when he talks of the white moderate “who constantly advises the Negro to wait for a “more convenient season.””