Re: Potted/unpotted...one more time!
Pickups without covers can feedback too.
On the other hand a pickup that is potted and doesn't feedback will have feedback problems if you put a cover on it without potting it a second time (with cover on) or otherwise putting foam or tape or chunks of wax some other soft material on the top of the pickup to stop the cover from vibrating.
Some makers like Jason Lollar and Jon Moore say that a properly wound coil should not feedback and doesn't need to be potted. (I'm not so sure, by which I mean that might also limit a winder on the combinations of tension wind patterns he can use.)
But the point is that both covered and uncovered pickups can have squeal problems.
