You know guys, lost in all of this is the fact that Vibrato is a wonderful tool if you can use it. Violinists use it in the same way, to fill out the note. Sorry to hear what the music teacher said. That's just wrong.
Many people wave their voices to hit a note, just the same way a swallow dips and rises before perching. It's an art and it works.
However, as I said before, it's distinctive and can emote as many negative as positive responses. No?