[thatwasunusual]

>> FYI, HTTP headers are case insensitive

> Since when are they case sensitive?

[...]

[thomascountz]

Perhaps the OG comment was misread or confusion was caused by a typo and/or edit.

When I originally read it hours ago, I also read it as "...HTTP headers are case sensitive," (emphasis mine).

That said, there is one caveat regarding case sensitivity for headers encoded for HTTP/2.