18.3.34 textEncoding - "The value is x-symbol means that the code points do not denote glyphs according to the semantics of [UNICODE] or another text encoding."
Actually two problems:
1) Unicode does not denote glyphs. It denotes characters.
2) Apparently if you use x-symbol, you don't mean characters according to Unicode or another text encoding. Makes me wonder why you would bother?
Actually three problems because the second sentence does not fit with the first.
3) First sentence talking about XML and various non-Unicode text encodings, second is not.
Suggest: "The value x-symbol means that the character encoding is not enumerated by Sec. 4.3.3 of [XML 1.0]."