I don't mind if a prossie comes on and makes a single post to put 'her side'. I will almost always believe the punter anyway, and if not only suggests he provide more details so we can get an objective picture. I try to point out that a review is only one review. If the prossie's any good she should be getting many reviews and they will balance out, and far more convincingly than anything she adds herself. This is a punting site and while a prossie's view on a punt might be interesting it is only interesting in a very minor way. We're interested in whether the punter enjoyed it. What she felt about it is her business, or maybe saafe's, not ours.
When the prossie comes on and starts flaming (or getting her mates to help flaming as happened to me on one occasion) then it gets a bit ridiculous. Like John Lewis sending insulting letters because you gave a bad review of their product -- no self-respecting provider of any sort of business does that and of course John Lewis doesn't and neither do decent prossies. Just makes them look stupid.
If a prossie wants to reply, here's some advice: take a deep breath, compose a factual, polite response offline. Don't take personal offence or display your feelings. Keep it to the objective facts. The review is an account of the punter's experience as *he* saw it, not you. Read it through while imagining you are the person who was pissed off with your service, see how it sounds (and remember they will almost undoubtedly have the last word). Remember that if you offer a good service that an incorrect accusation does you no harm. If there was a small mitigating factor as to why your service was not up to scratch you might want to mention it but not in a desperate way or thinking that makes it all right (the punter still paid his money and it maybe represents an awful lot more money to him than it does to you). Say what you think is appropriate to say in that *one* post. Leave it for at least a few hours and read it through calmly again. If it sounds polite, factual and level-headed, maybe post it.
Polite responses from prossies that add something and don't sound self-righteous are often acknowledged in a polite way. Repeat posts are less likely to be so well received. If the prossie comes on here just to argue she'll probably get kicked off and after making her case worse, so don't rise to the bait. If you didn't manage to make your point effectively, it's usually better to retire with dignity.
Don't tout, openly or subtlely (it is more obvious than you think). Don't complain to admin to ask for reviews to be deleted. Don't treat UKP as a chat room to join in as 'one of the boys' (you're a prossie, not a punter; use saafe for chitchat).
There are some valued UKP members who are prossies. They contribute occasional posts, often insightful, that use their experience as prostitutes to add something useful from the punter's viewpoint, not to respond to clients. It requires a great deal of maturity and few people are capable of it, but if you've been around long enough, genuinely care about punters enough, and can effectively put yourself in their place, maybe you have something real to offer. In which case, you will receive genuine thanks (as well as sharp criticism, in the same way that punters level at each other).
At the end of the day, in all politeness and fairness, remember this is a punters forum, created with much hard work for punters (not prossies) and on here, punters come first.