HTTP headers are ASCII not UTF8

[benaadams]

https://tools.ietf.org/html/rfc7230#section-3.2.4

Historically, HTTP has allowed field content with text in the
ISO-8859-1 charset [ISO-8859-1], supporting other charsets only
through use of [RFC2047] encoding. In practice, most HTTP header
field values use only a subset of the US-ASCII charset [USASCII].
Newly defined header fields SHOULD limit their field values to
US-ASCII octets. A recipient SHOULD treat other octets in field
content (obs-text) as opaque data.

So https://github.com/dotnet/corefxlab/blob/master/demos/LowAllocationWebServer/HttpRequestParser.cs
should be parsing bytes based on US-ASCII rather than UTF8 data

[KrzysztofCwalina]

Good to know. When we add validation to the code we will make sure non-ascii characters are handled properly.