Usually the offer of a free punt in return for bad service is a hollow gesture, mainly becuase they get refused last minute and because the punter doesn't want to return. If you had a shit meal in a restaurant and got diarrhoea - would you go back for free?
But that is the thing though. If someone went to a restaurant and got food poisoning and spent the night throwing up and then went onto tripadvisor and posted a dreadful review for that place.
If the restaurant owner then came along in response to that review and said, "am sorry to hear this. I will tell you what, how about to make up for all of this. You can come back and I will take 20% off your next meal with us". Like you say no sane person would ever return.
But if the customer said to that offer, "yeah, that's great, 20%, wow. I will be back on Friday just make sure you properly cook the chicken this time". This immediately gives the immediate undercurrent to the matter that the customer was maybe exaggerating things in his review from accepting this offer.
And thus the same thing could be applied here with prostitutes doing it; i.e A Punter comes onto the forum and leaves a negative. The girl comes along in response to the negative and says, "sorry about this, but if you come and see me again I will see you for £60 instead of the usual £100". And the punter then agrees. The girl will score from this offer on many different levels. As for one immediately the undercurrent will be there that the punter was exaggerating or lying about what went on in his negative given he has agreed to see her again after leaving it.
Then it also shows she is the 'good one' in all of this by offering to see him again and at a discount rate too after that punter has left her that negative (when really she has no intentions of seeing him whatsoever, she is just doing it as a PR exercise and a power play).
Then it also shows she is confident on her service she provides as she is offering him that booking on the basis he will come back and enjoy it.
Its a good power play for girls to use. And it is so bloody annoying that they have often no intentions of honouring it. If they are going to honour it, then fine. But if they are not, it makes it a disgrace given it in effect wipes the negative away from her doing it.