A simple single line, triple-quoted comment is giving syntax error. Why?

[Chris Angelico]

On Fri, Apr 3, 2015 at 4:40 PM, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> This sterile, pointless arguing about the minutia of pedantic definitions is
> not even close to useful. Honestly Thomas, Ian, nobody cares any more. If I
> were a betting man, I'd bet that neither of you can describe, in one
> sentence, what is the actual disagreement between the two of you, let alone
> why it matters for Python programming.

I know that it started in response to my statement that string literal
concatenation wasn't an expression as such, but I have no idea what
either side of the current debate is, nor how it affects my
statement's validity. I _had_ hoped it would reach some sort of
conclusion - I may be right, I may be wrong, but it'd be nice to know
which. So far... no idea.

ChrisA