On Tue, Sep 28 2021, Lars Ingebrigtsen wrote:

> Are there any additional steps needed to reproduce the problem?

No. But it seems, that Gnus does some whitespace-cleanup at some point.
Please copy from https://debbugs.gnu.org/cgi/bugreport.cgi?bug=50842
then it should work. Just keep all the whitespace.

-- 
           Peter