[Kalium]

In the US, a pattern of police doing so could be actionable.

It would be rather difficult for most American PDs to justify devoting resources to investigating somoene being mean online unless it was in a fairly narrow set of categories (clear and specific threat, harassment, etc.).

[foldr]

What's your basis for saying that it could be actiobable under the first ammendment?

It would be equally difficult for British PDs as far as I can see. But police in both countries don't always use resources wisely.