>> An example of such menu is mouse-buffer-menu bound to C-<down-mouse-1>
>> where the user might wonder what do these menu items with mode names mean?
>
> OK, but I still don't think I fully understand how context menus are
> different.  Are we sure the user will immediately understand the
> purpose of the context menus, but not of a buffer-menu?

Context menus displayed up by down-mouse-3 are ubiquitous nowadays,
they are everywhere, and the users expect them without a title,
unlike Emacs-specific menus unfamiliar to most users.

>> Using a text property would be a good solution.  Should then
>> the NS-specific "Select" title be removed in menu.c
>> when the title has a special text property?
>
> I'm not sure I understand what is the NS-specific "Select" title.  Can
> you point me to the relevant code?

I meant such patch: