So yes, you can arbitrarily pick one address of yours to share publicly and keep permanent. But there is nothing in the protocol or any of the default clients

So yes, you can arbitrarily pick one address of yours to share publicly and keep permanent. But there is nothing in the protocol or any of the default clients that gives anyone a distinguished "permanent address". So saying "I wish we knew Mozilla's permanent Bitcoin address" indicates that such a thing is expected, when in reality any one address that an entity has is a good as any other, and addresses are generally intended to be ephemeral and single use.