There is no clearcote on them, it's just glossy plastic and very soft crap plastic at that, i've got to do mine again, DJ LP is ok for it but it won't last long after it's been washed a couple of times as it's so soft.
Clear coat is pretty thin in these areas, so use a slightly lighter cutting polish or one with fillers. I assume your doing it by hand? DJ Lime Prime should be fine though.
Try some real fine polish, microprime sounds like a good one. If that doesn't work get a glaze/polish with some fillers in and then protect the area well. I f**king hate people like that who say ergh look at the dirt and then think it's a good idea to write their name in it! So un eduacted!
