Rogissimo, thanks. I think the Guardian/Observer convention just sort of ... evolved! It used to be that answers weren't given for the Radio Times puzzle - well, some self-appointed people decreed this! I gave an answer once, in ignorance of the 'convention', and was ticked off! That 'convention' seems to have died, faded away. The Guardian/Everyman one continues.
Norah, the site administrator, is definitely not a crossworder and she is happy when the site runs smoothly. The Guardian/Everyman threads seem to run themselves really. I think Norah would step in only if a request for an answer was greeted with a 'Not allowed'. As she has said before, this is a Crossword Help Forum. People can, of course, offer the level of help they feel is right. Some people don't give answers to prize puzzles. I give answers to most prize puzzles, though I prefer giving hints for the thematic puzzles.