It looks like no matter what if the last feedback you receive is negative then you will either have a ?? ? Trust score or a negative score. Look at TECSHARE for example, his rating from Vod means he has a question mark rating.
Also TF has a negative 9999 rating lol.
not always
I have seen users who received both positive and negative feedbacks and still has black trust ratings with first number 0
For example: my trust.