If you expect to be behind a reverse proxy that manages internal headers for you (removes them on incoming requests, and adds them based on internal criteria) t

If you expect to be behind a reverse proxy that manages internal headers for you (removes them on incoming requests, and adds them based on internal criteria) then accepting bare 0x0a newlines could be a security vulnerability, as a malicious request could sneak an internal header that would not be stripped by the reverse proxy.