Check it with a rag soaked in lacquer thinner. Rub on it and see if it comes off on the rag. If it doesn't safe bet it is just fine to leave there. A true "E" coat is the best base for your primers and paints you are going to find. The problem is whether the company who made your parts uses a quality "E" coat primer.
If it is insoluble (found with the rag rub test) I say you are in pretty good shape.
Another thing is if while sanding you hit bare metal on it, look to see how well it is hanging on to the metal. This goes for anything you are sanding for paint. If it looks like the edge of the feather is "sharp" and you could get a fingernail under it or something like that, strip it. If if feathers off nice, it is hanging on fine.
Brian
