Using amount risked in any calculation does not work for several reasons:
I don't think that amount-risked should have any weight towards the Trust-Value. For exactly the reasons you mention. I understand the intention behind it, but I very rarely see it being used for it's intended purpose and see it being abused much more often. In addition to that, the amounts required to have any weight are unlikely be thresholds that are hit, so that increases the likelihood that it will be abused more than used. Am I missing something or is that more of a liability than an asset?
At the end of the day it comes down to if you trust the word of the two leaving the ratings if it even happened that way to begin with, so IMO if the poster deems it a valid inclusion it could go in the comment area. It is not like anyone is going around verifying these values, and chances are if there is a conflict it will not matter much anyway as documentation of some kind is going to be required.