It is hard to talk about header fields without also noting they might appear across multiple lines via repeated names or obs-fold lines. My goal has been to describe the coalescing of fields in Messaging and only deal with complete values in Semantics. However, I think only obs-fold is specific to HTTP/1.x.

For now, we have the following text (currently in crefs) in the "Field Values" section of Semantics:

This document assumes that any such obs-fold has been replaced with one or more SP octets prior to interpreting the field value, as described in (xref).