HTTP関連のRFCで現れる `N#token` はカンマ区切りのリストを表す

1#header-token みたいなのは「少なくとも1個以上のheader-tokenがカンマ区切りのリストとして現れる」と読める。


A #rule extension to the ABNF rules of [RFC5234] is used to improve
readability in the definitions of some header field values.

A construct "#" is defined, similar to "*", for defining
comma-delimited lists of elements. The full form is "#element"
indicating at least and at most elements, each separated by a
single comma (",") and optional whitespace (OWS).

RFC 7230 - Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing