Guess different plastics are different (no big surprise, huh?).
As people have already posted with BMW-centric info, the following is just general FYI in case people with othe vehicles check out this thread:
The ones on my vehicles were never clearcoated. Yes, they have always been rather soft.
Some were actually painted, even though they felt/looked/seemed like they were just black plastic. This paint was *EXTREMELY* thin, as in "one gentle correction and no more".
Some modern polishes with "sharp" abrasives, even though they were gentle finishing polishes, left not-so-micro-marring that required a different approach to correct. Old-school diminishing-abrasive polish solved the issue.
In a similar vein, M205 left things looking great, even after an IPA wipe (that stuff just isn't right for this...) but they looked *terrible* a few days later after the Trade Secret Oils dissipated. Had to redo with something else.
The black plastic pillars on older Audis have withstood numerous polishings, by hand and machine, with zero trouble. But that sure doesn't mean that more modern Audis would be the same way.
Might want to LSP with a coating for marring resistance, though I do fine with heavily layered KSG (get over six coats on and the KSG will take the abuse, not the pillars' finish). Conventional LSPs can be OK if the material isn't too soft and you do the wash/dry carefully.
Much/most of my other black exterior plastics are the same sort of situation, though on some vehicles I just maintain them with ValuGard's Fast Finish, a product that somehow seems to give me the *exact* look I want on such materials.
Textured black plastic trim is another topic altogeter.
