Being realistic, I don't think admins will ever explicitly forbid trading accounts and ban everyone who tries to sell or buy an account, for the same reasons scammers are not banned.
If I'm wrong then correct me and in that case I'd ask them to begin with banning known scammers.
for those that say "scamming is allowed" I would respond by saying it is not explicitly allowed per forum rules. The forum will not moderate scams, while forum account sales are explicitly allowed per forum rules.
The fact something is "allowed" on the forum just means a user will not be banned because of that. It doesn't mean it's OK to do it.
I don't see much difference between not mentioning something and "explicitly allowing" something else. What's not on the rules is generally allowed, unless it's so obvious it's forbidden that it's not worth mentioning.
Anyway, if admins won't ban scammers then it wouldn't make sense to ask them to ban account traders. If they change their minds about that then please do ban known scammers.
That being said, I don't think trying to trade an account automatically deserves negative trust, and even less so being escrow for account trades. It deserves negative trust if the seller is helping scammer, either explicitly or by not doing something he could do.
For example if an old account with positive trust is being sold then that account could easily be used for an exit scam. If another Sr. account with neutral trust is sold then it would be much more difficult it's used to scam.
If a DT account is sold then there's a big chance it's used to abuse the DT system.
I would propose something less extreme: neutralizing sold accounts.
By that I mean accounts on DT should be removed from DT before being sold. Accounts with positive trust should lose that positive trust.
That could be done by informing of the sale to those who added that account to their trust list or left positive trust.
Those same users who were notified could then monitor the sold account for fishy behavior.
I want to say the seller should also check for the buyer trustworthiness, but that would probably be impractical as any untrustworthy user would just create a brand new account to buy another one.
The problem I see now with tagging every single user who tries to sell an account, or even ask a question on a sale thread, is that those ratings can dilute. I've seen sellers write "don't worry about my negative trust, it's just for selling accounts".
I don't think tagging everyone involved on account sales reduce the number of scams happening on the forum, and that should be the main (probably even only) objective of the trust system.
I agree with OP the rule regarding account sales is not clear enough. If we reach an agreement here then we can ask mprep to reflect that on the list of rules. If not then he could add something like "if you try to sell or buy an account you won't be banned but may get negative trust".