Accounts here are worth exactly 0 BTC, you should have no expectation otherwise. Your account could be deleted/banned tomorrow for absolutely no reason, without any sort of recourse. Just because we've come to expect a certain level of fair treatment doesn't mean its guaranteed. A more realistic example than Theymos deciding anyone with a vowel in their username is banned, is that signature campaigns could get banned from the forum (not immediately likely, but possible for the sake of argument). Would you be able to claim that you've suffered a financial loss in that case? People really seem to be forgetting that this is a forum... DT, trust, etc, no one outside of this little pocket of Meta users cares about any of it. Some users come here to discuss crypto, others frequent the alt coin section, some speculate, others want mining advice or technical help. If you aren't involved in the marketplace sections here, feedback should have 0 effect on you. We don't need to cater to those that discuss hypothetical situations that'd result in them being treated unfairly, the marketplace section is the only section that should have consideration.

That little grounding rant complete, I personally don't care about account sellers or those that choose to buy/sell accounts. I don't leave them negative feedback unless they are pretending to use the previous owner's identity to pull a scam, but I don't see why I'd have the right to tell people that they can't express their opinion on the matter one way or another, or that they can't leave feedback based on their opinion. If the problem is that users see any negative feedback as a blanket statement that someone will scam them the second they trade with them, thats not an issue with the system, thats a problem with the userbase. If I can leave people negative feedback because they like lemons, and it effects their trading in the slightest, we don't need to issue a rule saying that I shouldn't leave people feedback about lemons, we should issue a mandatory exam and pledge that people will think critically about all features of this forum before using them.

I am very against setting up rules surrounding what you can and can't leave feedback for. I'd much rather leave the interpretation of what constitutes a threat up to the individuals participating in a trade. If you think that being left handed is an untrustworthy trait, weird, but maybe I'll read your comment, agree and refuse to trade with a lefty. Otherwise, I'll disregard your comment and potentially ~ you if I find your ratings to be gibberish.  

Personally, I don't find people that default on loans deserving of red trust if they stay in communication with the person that lent them the money, and proactively make an attempt to rectify the situation. How many people do you think would be thrilled if I managed to make it a forum rule that you can't leave people negative feedback for defaulting on a loan if they stay active after doing it?