I know this is picking nits, but shouldn't the first sentence in section 5
(Deployment Considerations) have "already" and "are" transposed? In other
words, this:
Servers that do not support content codings in requests *are already*
required to fail a request that does use a content coding.
Instead of this (current text):
Servers that do not support content codings in requests already are
required to fail a request that does use a content coding.
I would also suggest dropping the "does" in favor of simply "uses":
Servers that do not support content codings in requests are already
required to fail a request that uses a content coding.
Apologies in advance for nitpicking.