If you do not have a good enough feedback score yourself, you cannot affect others scores. This is why your feedback goes into the 'Untrusted Feedback' section, rather than the Trusted.
If you get tagged by someone on Default trust in a positive way, I believe that you can then influence trust scores yourself.
You are confusing between trust feedback and being in trust list. Former shows up in your profile, while the later gives you the power to be shown in other's profile.