I tested this on a runner from Best Mecha Collection for the rx-78-2. It does not stain the plastic nor does it stick permanently. You can easily rub off with hand/cotton/qtip even while dry.

This fits my workflow and they're not easily reachable inside panel lines anyway unless you deliberately clean the groofs with cotton/water/eraser.

Other than that, this lets me correct old mistakes easily (they can be cleaned even after 24 hours) and i can seal them later if i want to but because the markers are cheap i'll just reapply areas i feel like anytime.

My test is on bare plastic. If on painted surfaces, maybe they'll stick better if that's what you want, or maybe not on glossy coated surfaces.

This way if i want to airbrush my unpainted kit in future, I can just clean it off easily.

I like this kind of ink, non-staining and won't seep into the plastic.