Let's take the example of someone who came to this forum with the intention of scam as many people as possible, other members recognized this and left negative feedback which is then clearly visible in some parts of the forum. But what if that same member uses his signature to scam by posting on boards where trust is not shown?
Maybe I didn't use the best choice of words. Maybe "less necessary" would be more appropriate, or something like this:
It is visible where it's needed the most — in the Marketplace board and its child boards and in the Trading discussion board and its child boards.
And in regards to your example YES, you are right... but had to think of a corner case in order to make your point. This is not the usual
modus operandi.
First of all newbies cannot add link in the signature. So would have to rank up or buy copper.
Then by the time our newbie investors from the bitcoin discussion board get a chance to see his signature enough times the user would already have red trust, flag, messages with BEWARE ! SCAM ! after most of his posts and eventually even get banned/nuked (even if scams are not moderated he would most likely manage to break some rules around here)
I am not saying it would be wrong to display trust ratings in other boards too, it's just that I don't see it as that big of a necessity tbh