2822upd-04 section 2.1 states in part:
Note: Common parlance and earlier versions of this specification
use the term "header" to either refer to the entire header section
or to refer to an individual header field. To avoid ambiguity,
this document does not use the terms "header" or "headers" in
isolation, but instead always uses "header field" to refer to the
individual line and "header section" to refer to the entire
collection.
"individual line" is technically incorrect. Either "individual field"
(preferred) or "logical line" would avoid the difficulty.
Section 2.2 begins with:
Header fields are lines beginning with a field name, followed by a
colon (":"), followed by a field body, and terminated by CRLF.
I suggest beginning the sentence with "Header fields begin with a field
name at the start of a line," and continuing after the existing text's
first comma [same issue as above].
Section 2.2.1 contains:
Semantically, unstructured field bodies are simply to be treated as a
single line of characters with no further processing (except for
"folding" and "unfolding" as described in section 2.2.3).
I suggest changing "single" to "logical" [same issue as above].