* 2020-08-03 09:13:35+03, Teemu Likonen wrote:

> I believe the header part can be switched to left-to-right mode by
> using function bidi-string-mark-left-to-right.

It seems that adding just a single U+200E LEFT-TO-RIGHT MARK character
(possibly with invisible text property) in the beginning of message
header paragraph will do. The attached (inline) patch does it.