OK to put comments before the XML declaration?

Question

Is it OK to put comments before the XML declaration in an XML file?

<!-- Is this bad to do? --> <?xml version="1.0" encoding="utf-8"?> <someElement /> 

Answer 1

No, it's not OK.

Appendix F of the XML spec says:

Because each XML entity not accompanied by external encoding information and not in UTF-8 or UTF-16 encoding must begin with an XML encoding declaration, in which the first characters must be '< ?xml', any conforming processor can detect, after two to four octets of input, which of the following cases apply.

Ah, but, section F is non-normative, you say.

Well, section 2.1 gives the production for a well-formed XML document, thus:

[1]     document       ::=       prolog element Misc* 

...and in section 2.8 we get the production for "prolog":

[22]    prolog     ::=       XMLDecl? Misc* (doctypedecl Misc*)? [23]    XMLDecl    ::=      '<?xml' VersionInfo EncodingDecl? SDDecl? S? '?>' 

So, you can omit the < ?xml declaration, but you can't prefix it with anything.

(Incidentally, "Misc" is the category that comments fall into).