I can see chrome being a problem because you have to dip the whole part in chrome and everything will attract the chrome chrome plating. There might be a way to mask it but it'd be news to me. This is why Robin can't chrome his engine block or head.
A chrome valve cover with chrome on the underside there's a chance the chrome could flake off the inside and cause problems. But with powder coat... it's just like paint. Mask, spray but then you need to put it in an oven. The only thing that could potentially cause problems would be the heat from the oven but AFAIK with a home powder coat kit you can use a household oven, it doesn't take major heat. No more than what the valvecover would see, for instance, bolted onto a cylinder head under the hood of a turbo 4 banger.
The only other problem I could see would be improper prep. Say hosing the thing down with a sandblaster and glass bead then putting it on without fully cleaning it. Then a clump of sand or glass bead comes loose from inside and falls in the oil. But the solution to that is just make sure you clean the thing properly and be careful with the media blaster. If you mask before glass bead/sandblast the masking should stay intact and maybe only need a little touchup.
