Dispite my disagreeing with you and feeling pretty shafted by the removal of Parler, don't take it personally - you're an open source contributer who has earned my respect.
Yes, after concrete evidence that the incitement is sincere, or being materially interpreted as sincere.
(For the record: I think the guillotine imagery is as offensive as the Pinochet helicopter stuff, which is to say, extraordinarily offensive, and I think less of anyone who uses it. That's easy for me to say though, because I'm also not a leftist.).
Did they name people, places, or times? A key factor in free speech legal cases is how credibly threatening something is — someone telling a friend “I’m going to strangle you!” after they get rickrolled is clearly not but someone saying “On <date>, we’re going to <place> to kill <politician>” is enough that the Secret Service might want to talk with you.
Another factor is the climate: nobody is using guillotines anywhere now but mass shootings are sadly common.
Is that so? Curious, because I was seeing a lot of guillotine memes from leftists last month.