The phrase "Since the HTTP specification (section 3.7.1) defines a default character encoding of ISO-8859-1," is inaccurate. That default only applied to text MIME types (e.g. text/plain) and not to application MIME types (e.g. application/fhir+xml). The "HTTP specification" is not defined, but appears to be RFC 2616 based on the subsequent text. That RFC was obsoleted in 2014 by RFC 7213, which explicitly removed the reference default character encoding (see RFC 7213 Appendix B). For both reasons, this phrase should be remove.