I am looking at TS-466 (Multiline headers are not preserved) and as far as I can tell this is by design. The field parser in MIME.cc goes to some effort to detect this situation and then strip out the intervening whitespace, including the CR/LF. So something like
Accept: text/html, text/xhtml becomes Accept: text/html,text/xhtml Is there any purpose to this? Why would something think this was making an effort to achieve? The multiline format is explicitly allowed by the HTTP spec and the parser code specifically checks for it so it can alter the field value as shown above. Is there any reason to not preserve all the interior whitespace? I presume (haha, foolish me!) that the field value parsers skip over the whitespace.