Well why don't we look at the effects of getting a negative trust report from someone on default trust list. Assuming you do not have preexisting trust feedback to overcome the negative trust then you will get a trade with extreme caution tag. If you are someone who engages in business that requires an extreme amount of trust, for example someone who deals in gift cards or may need to handle personal information then yes this tag would be detrimental to your business. If however you engage in business where transactions can easily be moderated by some kind of trusted escrow service then all a trade with caution tag will do is get a person's customers to want to use escrow more often. As these people make more deals the positive trust they receive will outweigh one scam report from one user (if one person gives two or more scam reports on the same person it will only count as one).
A honest person can buy a new account with fresh neutral trust in the event it is tarnished beyond repair as you describe would happen. IMO a honest person is actually more likely to do so then a scammer because a scammer is risking the purchase price of the new account for when they get caught again while an honest person with an unjust scam rating intends to continue to operate honestly moving forward.
I personally think Vod giving negative trust by jumping the gun like he originally did in the case discussed in the OP is an exception to the rule.
I would disagree that "lying" is not a valid reason to give someone negative trust. If you are lying about how much bitcoin you have or about your prior trade history then you are trying to get your trading partner to be more comfortable with you which would potentially make them more vulnerable to get scammed. In order to scam someone you obviously need to lie at least one time in order to get the other person to give you money in the assumption they will get something in return.
Regardless of your assumption that a negative rating does not inhibit trading, it does in fact do so. People in this community are already SO PARANOID about getting ripped off, that all some one has to see is the red rating and their brain turns off, and they move on. It does IN FACT destroy ones ability to trade almost completely.
I love also that your supposed solution as some one who peddles other people's trust is for honest users to buy another account. Self interested much? Further more even if an honest user did try to buy an account his immediately puts them under suspicion of being a scammer and from that moment on they will be treated as such. It is well known that a lot of the account sales are either run by or closely monitored by staff so they can keep lists of scammer suspects. All this would do is make that formerly trusted user enter further into the realm of being suspect, and at that point why try to be honest if everyone is making it so hard and treating you like a scammer?