I currently have to maintain an out-of-tree patch for openssh (in Debian, and probably elsewhere).

The rationale for this patch are the two merged bugs (#313317 and #408029) in Debian:
the environment variables sent by AcceptEnv/SendEnv functionalities
should take precedence over PAM variable settings, especially for
locale and terminal related settings (or commands that are
locale-sensitive or terminal sensitive might give incomprehensible
gibberish as output to the user). TERM is already managed in a special
way, but not LANG or LC_* variables.