When I ask for criticism it is from people whose opinions I respect., not people on the net that do not provide any evidence of theirown singing[ example amongst others the anonymous troll on the shirley collins thread]   
for example some while back I aked MGM to listen to a recording of mine, and I took some of his criticisms on board, when I was working in a duo with Richard Grainger we would ask each other opinions on songs we had just written.
when I get unsolicited criticism from people[ in the real world rather than internet forums]whose opinions i do not respect, I listen politely and say nothing.
"Lesson being, don't rely on applause as an indication that your singing is any good."
Not always true.It is often an indication that you have communicated with an audience.
in my experience audiences do sometimes know when a performer has sung really well, to suggest otherwise is an insult to audiences and their critical faculties, I remember performing a song at The Wilsons Folk club, and the song went really well, the audience realised it too., considering the high standard of singing at that club, I think it would be grossly insulting to suggest that they were applauding for any other reason than the song had been performed well.
"Audiences (in general) want you to succeed and will reward a singer for effort - for the best reasons."
no, it depends on the audience, they all differ, that statement can apply to people who come on as floor singers who are clearly inexperienced but have potential but who are nervous., but in my opinion that is about all it applies to.
the higher the standard of singing in a club in my experience the more critical the audience, are particularly if the audience consists of lots of good singers.