1. The "request" line in HTTP is not a header - it is the request, which can have associated headers. The headers are all “about” the request. The request itself is not a header, and does not follow the header syntax. (The historical reason for this is that the request line was defined in HTTP 0.9, which did not have headers.)
2. ISO-8859-1 is not “a crappy Windows character set”. It is an international standard specifically different from what Microsoft was using at the time (code page 437 was standard for MS-DOS in the US). Later, Windows switched to code page 1252, which is a copy of ISO-8859-1 except some extra glyphs in the bytes the ISO standard defined as control characters.
I mostly referred to it as a "crappy Windows character set" because A) it has a limited set of characters, mostly Western European, and B) it's pretty much only used by Windows these days. While the term "crappy Windows character set" is not perhaps entirely accurate, it is a short, tongue in cheek summary of ISO-8859-1.
(Apparently you weren’t thankful enough to upvote. EDIT: never mind, I must have been mistaken.)
A more accurate description of ISO-8859-1 would be “a crappy 8-bit character set mostly only still relevant for Windows which uses its own embraced and extended version, CP1252.”
I've changed the wording to be slightly less ambiguous. Thanks again :)