I'm not sure what you dispute or your point is here. If people slightly or strongly start aping Trump's writing style in various forms I'd say there's a good chance those people are right wing or simply "not the same people writing in all lowercase" you know?

You highlight stylistic choices. I'd say we can observe the differences in different styles and see how uses them. Is Trump writing in all lowercase? No. Is this poster writing like Trump? No. Do a lot of left-wing people use the all-lowercase style? I see it all the time, yes.