Let's not get too cynical - I think we all know the difference between friendly applause and enthusiastic applause, those of us who are prone to self-doubt especially. When I first went to singarounds I used to listen intently to the length & volume of 'my' applause and everyone else's, as far as I could mentally compare them; if mine came out in the top two or three, that was a good night. I'm not so anxious now (and I enjoy the actual singing more as a result) - although I still live in fear of the Polite Ripple.

Conversely, being negative isn't any guarantee of sincerity or good intentions. There's a song by Ed Kuepper with the chorus
"Then I realised that my harshest critics can lie
And they don't even have my best interests at heart"
It changed my life in a small way - before I heard it that thought had never crossed my mind. True though - someone who tells you your singing is crap may not be trying to help you improve; they may just not like your singing (or indeed you).

If anyone's curious, here's some of my singing. Practically perfect in every way (I don't think!).