huseyinfiliz
I think you've hit on a lot of it.
a few things I'd add and/or change:
1- users should be notified when feedback is left for them using the default notification system. perhaps even allowing the user to be sent a private message (using byobu) or an email as well - all configurable.
2- I just thought of this one as I'm reading through this discussion. maybe once the user hits a certain amount of feedback, they get some sort of sticker or badge like other selling platforms do...although I don't know if that is redundant or not because their actual feedback score/number could be seen as just that too.
3- I personally prefer the feedback rating as positive/neutral/negative, but I can see how someone might prefer a star rating or a more granular approach, like 1-5. perhaps allowing configurable options would be ideal here.