is there any real rule whether to put an empty space between a field
name's colon and the field body?
It's common behavior to include one here,
but it's unclear - or even purpose (A.5.) - that none is required.
According to obsolete A.6.3 WSP is (or was, according to B.21.) even
allowed between header field and colon.
There may be special rules for special header fields, but to my knowledge
there's none for all.
Is the leading space of a field body part of the field body or not?
There's only a rule for folding WSP in multiple line field bodys.
Thus any current leading space should be part of the field body.
Is there any need to improve this description?