I actually just ran into this problem which caused me to scratch my head
for too long:
I actually am working on a project where I want to use this syntax. I
don't have to do it this way, but it's pretty self documenting.
Once again I forgot about the '# ' rule. This was actually one of our
original, albeit yagni, use cases for comments. Now it's broken.
Clark told me on the phone that he doesn't mind:
for directives. Steve and Why don't even emit the #YAML directive by
default. And I'm about to follow suit.
Using %DIRECTIVE:foo frees us to use:
whitespace + '#'
for a comment (where whitespace includes newline and start-of-stream).
PS Yes I know I'm finally giving up my precious little '%', but I still
got '@'! ;-)