Petr Baudis [off-list ref] writes:

quoted

Still, why would you escape it? My shell will not take # as a
comment start if it is immediately after an alphanumeric character.

I guess there MIGHT be some command shell implementation
that stupidly _DID_ accept "#" as a comment character,
even immediately after an alphanumeric.
If that's true, then using # there would be a pain for portability.

But I think that's highly improbable.  A quick peek
at the Single Unix Specification as posted by the Open Group
seems to say that, according to the standards, that's NOT okay:
http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02
Basically, the command shell is supposed to tokenize, and "#"
only means comment if it's at the beginning of a token.

And as far as I can tell, it's not an issue in practice either.
I did a few quick tests on Fedora Core 3 and OpenBSD.
On Fedora Core 3, I can say that bash, ash & csh all do NOT
consider "#" as a comment start if an alpha precedes it.
The same is true for OpenBSD /bin/sh, /bin/csh, and /bin/rksh.
If such different shells do the same thing (this stuff isn't even
legal C-shell text!), it's likely others do too.

--- David A. Wheeler