I've yet to try this but I reckon another way to leave negative feedback without risking getting even retribution is to leave it just before midnight on the night before it expires. The opportunity to leave feedback expires after one month of the booking date, so if you had a booking on 5th October, leave feedback at 23:59 4th November. The escort will not have opportunity to respond before their chance disappears.
I'm making the assumption there the expiry isn't extended upon receiving feedback but since I've not tried it, I can't vouch for it.
Never been that bothered to be honest, but those with a grievance may wish to give it a spin - see if it works.