This topic actually got me wondering, should we really only limit "trust" for trade-related purposes?
Doesn't it follow that if you are a known scammer by virtue of your market trades, then that your words (posts) are also questionable? I assume that scammers are understandably biased to say things that would be in their favor (or for their profit) and therefor also cannot be trusted.
I think so. Newbies will likely judge users on their trust rating, and not heed their perfectly sound advice/post. Anyway, not every user is rightly tagged, and negative trust ratings are subjective. What I might consider untrustworthy could be different to you. Just because someone on DefaultTrust has left a negative doesn't mean they are actually right.
You could give Deathandtaxes as an example. They were very well informed about Bitcoin, and offered some very intellectual discussions about it. However, they have been red tagged.
On the other side it sometimes helps distinguish trolls and people you shouldn't waste your time with. I've previously seen people 'talking bollocks' in Bitcoin Discussion and wasted my time trying to engage them and then when you then see their profile and it's littered with red you suddenly realise they're a troll and that's all their account is good for now. I'm not saying that trust should be shown everywhere, but I get the reasoning why it's not shown because it will effect how you perceive that person (though sometimes knowing their 'true colours' can be helpful).
This is a good point. This is kind of why I liked the ignore glow effect that was shortly implemented a while back. The more the user was ignored the more glow that was added, and what colour the glow effect was. That was good for distinguishing users that aren't worth listening too. This did have its drawbacks which resulted in it getting removed, but I feel that this was better suited than the trust system in identifying trolls.
Why doesn't merit work to distinguish this though?
Merit probably isn't the best solution to identifying trolls. Several members started off with high amounts which would be misleading to those that are new to the forums. Plus, merit is rewarded subjectively, and I've seen several posts that have been merited even though they don't deserve to be. Take for example the multiple bounty threads which have received merit.