Bookworm's /etc/mailcap seems to break s-nail

[Jesper Dybdal <jd-debian-user@dybdal.dk>]

I use s-nail as my mailx command (selected using the Debian 
"alternatives" mechanism).

Since I upgraded from Bullseye to Bookworm, s-nail now shows a bunch of 
error messages in connection with viewing messages.  Here is a sample:
> s-nail: $MAILCAPS: /etc/mailcap: x-scheme-handler/mailto: ignored 
> unknown string/command: u = \\${u//\\\\\\"/\\\\\\\\\\\\\\"}
> s-nail: $MAILCAPS: /etc/mailcap: text/english: ignored unknown 
> string/command: then exec emacsclient --alternate-editor = 
> --display=\\"\\$DISPLAY\\" \\"\\$@\\"
> s-nail: $MAILCAPS: /etc/mailcap: text/plain: ignored unknown 
> string/command: then exec emacsclient --alternate-editor = 
> --display=\\"\\$DISPLAY\\" \\"\\$@\\"
> s-nail: $MAILCAPS: /etc/mailcap: text/x-makefile: ignored unknown 
> string/command: then exec emacsclient --alternate-editor = 
> --display=\\"\\$DISPLAY\\" \\"\\$@\\"
> s-nail: $MAILCAPS: /etc/mailcap: text/x-c++hdr: ignored unknown 
> string/command: then exec emacsclient --alternate-editor = 
> --display=\\"\\$DISPLAY\\" \\"\\$@\\"
> s-nail: $MAILCAPS: /etc/mailcap: text/x-c++src: ignored unknown 
> string/command: then exec emacsclient --alternate-editor

I have no particular wish to learn about /etc/mailcap.  The only way 
I've found to avoid this is to remove the /etc/mailcap file entirely.

The package versions involved are:
* in Bullseye:
   mailcap/oldstable,now 3.69 all [installed,automatic]
   s-nail/oldstable,now 14.9.22-1 amd64 [installed]
* In Bookworm:
   mailcap/stable,now 3.70+nmu1 all [installed,automatic]
   j-nail/stable,now 14.9.24-2 amd64 [installed]

Has anyone else seen this?

Thanks,
Jesper

--
Jesper Dybdal
https://www.dybdal.dk