UNFAZED
Bit of a truce here 'cos I'm not getting at you and I understand fully where you are coming from.
My wife has had a problem landing - well not really landings just rounding out - try as she does she just cannot get it to 'click'! and of course the more people who tell her the 'trick' of rounding out the more difficult she finds it.
She has done all her exams and all her training up to XC but at 80 hours this little bit has eluded her.
Currently she is with the MSF and they have taken the attitude 'let's skip that bit and carry on with your training then come back to it later'. She has ended up a competent flyer and now feels ready to fly on her own, I think it is only the weather that is preventing this.
It would have been very easy for an instructor to have told her a long time ago to give up if the opinion was based only on her ability (or lack of it) to go solo.
I suppose you may consider that she is actually capable of 'flying' solo, what she can't crack is 'rounding out' in the landing phase
I accept that your own observations on ability would be based on the student's overall flying ability and not just one part where something hasn't 'clicked'. In which case I agree that your reservations should be passed on and the student would then have to make his/her own descision about their continuation.
I do think, however, that if you are asked to give instruction to a person who is aware that they will never qualify then you should be happy to do this and not consider it a prostitution. You will achieve a 'result' not necessarily an exam pass but the result that the person concerned wanted. After all you are happy (I assume) to give 'air experiences' to many people who have no intention to study for a flying qualification