"Apart from silent prayer, a woman was arrested for holding up a sign saying that coercion was a crime and offering to talk to anyone who wanted to. Is that intimidating?"

Depends on the context. Body language etc. But the main context is probably they were gathering in a place where it is forbidden to gather. Not arrested for praying or holding up signs.

Precisely this - it's the being there that was forbidden, not the act of praying - I'm not aware of any modern case where such a thing has been proscribed (at a guess, I would have said the last time was probably around the era of Cromwell, without checking).

Being there was forbidden for a specific group of people because they had a track record of harassing behaviour, much like a restraining order will likely be granted if someone has a track record of abusive behaviour towards another person. The praying thing is always mentioned as it makes it sound like some astonishing intervention in personal religion, while in reality, it's a complete red herring designed to rile people of a pre-existing viewpoint.