Here's a patch (although this is sent with gmail - don't ask - and it might be mangled beyond recognition):
diff --git a/lisp/man.el b/lisp/man.el
index 4b23530..24daca1 100644
@@ -1177,7 +1177,8 @@ See the variable `Man-notify-method' for the different notification behaviors."
;; \255 is SOFT HYPHEN in Latin-N. Versions of Debian man, at
;; least, emit it even when not in a Latin-N locale.
(unless (eq t (compare-strings "latin-" 0 nil
- current-language-environment 0 6 t))
+ 0 (min 6 (length current-language-environment)) t))
(let ((str "\255"))