Hello,
I've received confirmation from 3 or 4 users that they've submitted Trust feedback on my profile, but I am still seeing "No Feedback" in my trust area. Is there some kind of limit for new users?
The approach you are using is wrong. You are not supposed to expect or ask anyone to leave you trust feedback just because you left them a postive feedback. The users or people should leave the feedback when they feel like without being pressured to do so otherwise it will look like those artificially made reviews you see in some websites.
Trusted feedback only appears if the person who left you the ratings is a DT(Default Trust) Member or if the person is in your custom Trust list.