Bryan,
"All we can possibly know beforehand is that they want to sing or play."
There was never any question (certainly not as far as I'm concerned) that any singer who wished to was given one bite of the cherry; as you say, how else would we know whether they could sing or not. The argument is about whether people who wished to sing were consistently given spots before they had conquered the rudiments. SHOULD PEOPLE BE ENCOURAGED TO PRACTICE IN PUBLIC?

"persistent bad singing isn't a problem...... "
As I said before "ding-ding; I'm on the bus" Not to you maybe, but others suggest that it is to them. But the question has to be; is the best place for singers to overcome the rudiments of singing, in front of an audience? Apart from the effect that a non-singer has on the other residents, what image of the club – and folk song in general – does a visitor take away from a club which persistently presents singers who can't sing? Is it unreasonable to expect a 'singer' to be able (at the very least) to hold a tune and not to have to rely on a text to get through the song before they sing it in public?

"..... because (they believe) they're worth it, and if you believe that, there's a good chance you are".
I have persistently argued that virtually anybody can sing, but I have always qualified this by saying "if they put the work in first".

"Yes, we have singers who are, perhaps, somewhat short of concert standard"
Again you are dodging behind phrases like 'glass ceilings' 'virtuosos' and 'exclusion'. The argument has never been about singers reaching "concert standards" before they perform in public; it has always been about mastering the rudiments.

"hit-and-run".
Sorry – a knee-jerk on my part, made when this thread was generating more heat than light – I apologise.

"By making our criterion the desire to sing, we are raising standards".
Not if you are consistently putting on (or urging others to put on) singers who can't master the basics you're not.

" Not by selecting the few who are good enough but by helping everybody to get better and, in my experience, they do."
Again, loaded phraseology – nobody has suggested that only 'the few' are good enough to sing; we are saying that in order to present our music in a good light, basic standards should first be achieved.

""not in my (admittedly now somewhat limited) experience I'm afraid" That is, I think, the nub of the problem......"
I left the club scene principally because I believed that the 'near enough for folk-song' crowd had finally taken over the asylum. Arguments like this only serve to convince me that I was right.
I have no doubt whatever that there are clubs where the standards are high enough not to give the impression that folk singing is artless and inept; nor do I hesitate, on the basis of what I've heard, to include your club among the better ones, but that doesn't change the fact that clubs I have visited confirm my experience and that of others I know far more familiar with the UK club scene.
I have heard it argued on this forum that not only are standards unnecessary, but they are undesirable, the inference being that the music is really not worth the effort – not for me I'm afraid.
Jim Carroll