>people who have concerns different than mine

"Trying to abduct my child either directly or by proxy" is not merely a question of polite differing concerns.

Who is trying to do that?

People who call CPS just because children are outside unaccompanied? It's obvious taking children away from the parent is a possibility when one makes that call.

OK, but ... those people may not be 'concern trolls' at all (whatever that means).

I think in this case ‘concern troll’ means someone who can’t mind their own business and chooses to troll someone by stirring up unnecessary drama or conflict, using insincere concern as a pretext.

We know the concern is insincere because the OP’s example (children playing in their yard) cannot be considered concerning by a reasonable person.

I think you're creating a fine definition but based on context and your own intellectual sophistication; we don't know what the author of those words meant.

Based on my experience with children who actually need protective services help, calling about kids playing outside is not even close to getting a home visit let alone anyone taking your kids. Maybe it happens, but not in my east coast state.