A user left me negative feedback, but we worked it out and they would like to remove the negative feedback. But neither of us knows how to do that. Is it a case of having the user message a moderator and having the mod change the feedback?

Thank you for your time.

QED2

Can confirm here that I am trying to change feedback for above user. I had no idea if it is not possible. Please let me know how I can change it if an issue becomes resolved at a later time

On the trade's page, there is a Support / Dispute link you can click. An admin (sebi) can change the feedback.