Nice thread but this point is not true.
-Usually buying conf keys from my local reseller, once cuz of mistake he ordered 2 conf keys to single account, received both and both was valid.
So its possible that false seller order 2 conf keys, give 1 of them to buyer, new owner change registration, ordering new own confirmation key, create new recovery key from it, and still getting hacked like 4 months later.
Fact is account stay on his data so he could order just new conf key but he might lost items/get banned or rooked character before getting new key.
So the only safe way is to buy accounts that:
-have no recovery key ordered in payment history for last 6 months,
-seller could provide letter / screenshot/scan with used confirmation key to check if it was really used (since working just once),
-buy from trusted seller that check point 1 & 2 since most ppl don't even know they could check payment history and think that once registration is change account stay safe