"...Unicode has been standardising CJK character sets" - CJK characters sets are complex, and will always face opposition, besides, this is less related to how the characters are encoded, and more how to choose and composite your code points.

"I think the author has confused the fixed-length UCS-2 and the variable length UTF-16." - No, in the same sentence you are quoting he mentions that utf-16 is limited to 0x110000 codepoints, contra utf-8 that is specified to expand up to 6 bytes.

"Not true. NUL is a 16-bit character in UTF-16. Use a C compiler that supports 16-bit char width." - I won't be converting my source code into utf-16 any time soon. Besides, C is not a good example where this is an actual problem, the "unicode strings" will still just be represented as binary blobs - different depending on which encoding you choose. It's more of a problem in e.g. Python, where the native string is an array of characters, not just a null terminated blob. I wouldn't encode my source code in utf-8, however, if my editor my default happened to support utf-8, this wouldn't be an issue unless I enter an non-ascii compatible code point. I see this as a big plus.