While we are at it, why not limit the number of negative ratings that one user can give to another? Some sane limit e.g. 20 would be sufficient (AFAIK there has been no case where 10 was legitimately hit let alone more).
Instead of limit , a trust feedback cool down meter can be implemented. You can give only one feedback a day to a specific user. This will help in reducing trust spamming where a user is giving 50 long feedback in a day to a single user.
For length, I like the idea of view more, or fix the length of trust feedback and user who like to write more can create a post and link to the feedback.