I think that as it is now it's much better.
Because when you dealt with someone before 5months why do you want to change it now?
Especially when you want to change from positive to negative that could change the trust number too much if the feedback was old.
You can simple delete it, or make another one (positive or negative or neutral)
but if you mistakenly deleted the positive feedback 5 month old, that you new feedback will not be the same value(score)