Not sure yet about your last point Ed, but I typed the following yesterday then events caught up with me & I didn't get a chance to post it, so I'll throw it in anyway...
With regard to the "Listener", I think it's just one of those things that there's always been an unwritten rule on the Web that people shouldn't ask for help. The same applies to the "Great British Quiz" (I think it's called) -
it's just not the done thing to ask for assistance. I have no idea how this came to be in the first place but have no gripe whatsoever with their "off-limits" status.
Of course, being a Q & A site makes it nigh-on impossible to police these subjects & the Topics in general without being accused of censoring the right of free speech.
On the whole, I don't believe there should be a problem if someone posts a thread titled "Listener XXXX - I really enjoyed this!" with a discussion by its solvers to follow. If someone then posts a request for help with 1d, thereby breaking that "code of etiquette", barring a gentle reminder that it's "not the done thing", I doubt the regular AB Listenerites (?) would post answers, but what's to stop an observer from joining & doing just that?
I recently stumbled on a site (& unforgivably failed to bookmark it!) that slated AB in particular for just such "slips", if we can call them that. I haven't seen any such but *am* guilty of not looking at every Listener thread. I stopped sending them in years ago when I just lost interest in them - particularly the maths-based & Playfair ones - hateful!
anax - although appreciating your personal viewpoint regarding full answers to Prize Cryptics, as Mamya indicates, they often have to be received back by post pretty quickly, whereas a quiz might have months to run. Quite a few AB'ers - particularly those new-ish to cryptic solving - have mentioned in the past that they appreciate the full parsing of an answer as it helps them learn the craft.
As to quizzes (although I do so few my opinion might not matter), I think those that have a flat-out "no-asking" policy or until a certain date are within their rights & would like to see such requests observed.
Asking for extra clues rather than outright answers seems ok to my mind. For the most part I tend not to answer Quiz Qs simply because I don't wish to upset anyone on either side of the argument - just as Dave says, "if in doubt, say nowt".
I believe a large part of the problem stems from the fact that some people seem simply too impatient to finish the puzzle/quiz on their own, being overly-keen to post their entries despite the quiz having weeks or months to run & often having to ask only a few Q's from a list of many, thereby proving that they're capable solvers.
Of course, the whole thing is an unwinnable Catch-22 situation that will never be solved to everyone's satisfaction.