We could however, make it bannable and thus more risky for the people who engage in these trades (issue a permanent ban for both the seller and buyer).
Providing that work is done on the quality of posts here, I can't say I would see the need for this to come into place. While account trading is inherently untrustworthy, and should by no means be supported by anyone, providing that an account follows the rules of the forum and has no prior reputation (E.G Positive trust/DT etc) I do not see a problem with it changing hands.
In addition, I feel that it may simply be useless work for Staff members; if the seller has any sense he will sell the account using an anonymous Newbie account. Banning this will do nothing but waste the time of Staff.
A common misconception by ignorant users. There is zero reason for one to trust an account by default just based on their rank.
The fact that this misconception exists however shows that it is a problem, regardless of the stupidity of it.