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2.1 Document conformance, second last paragraph - Suggestion
UTF-8 or UTF-16 and no encoding is specified by a higher-level protocol
UTF-8 or UTF-16 and no character encoding is specified by a higher-level protocol.
Just a suggestion for future versions, more precise.

C. Deployment Advice, somewhere in the beginning - Grammar, Typo
If a document author wants to facilitate such validation, they may include ...
If document authors want to facilitate such validation, they may include ...
Most of the document uses authors instead of author, so authors might be consistend, so the plural of they can be used.

C. Deployment Advice, last paragraph
that includes a reference to the RDFa Initial Context IRI http://www.w3.org/2011/rdfa-context/xhtml-rdfa-1.
Should this be? ...reference to the XHTML RDFa Iniatial Context IRI ...
From my unterstanding the RDFa (Core) Initial context is http://www.w3.org/2011/rdfa-context/rdfa-1.1.

F.2 Informative references, Date on SGML Catalog - Typo
10 september 1007
10 September 2007
To be consistend with capital letters on the other references for the month and to refer to the right millenium 2xxx instead of 1xxx.

My initial context issue
Quote: HTML+RDFa uses an additional initial context by default, http://www.w3.org/2011/rdfa-context/xhtml-rdfa-1.1, which must be applied after the initial context for [RDFA-CORE] (http://www.w3.org/2011/rdfa-context/rdfa-1.1).

I wonder, if the "initial context thing" could be described a little different, from my understanding, it is a collection of TERMs, that should be known to processors by default, but the child has a different name, that is not, let's say, self explaining. On the other hand, there is a initial context, that is produced like in 7.2 of RDFa core. So actually the document initial context is just a part/source for the initial context. "TERMs for intial context" would be more precise for the initial context documents of XHTML+RDFa and RDFa Core.