Delete = \177 = ASCII? Perhaps I'm confused by "as X11 calls
  it".

I meant:

In the ASCII character set, there is a character called DEL, and it is
\0177.  Real terminals have a key with various labels that send this,
and it's generally the "primary delete key", above/right of return
where it's easy to type.

There are "extended or numeric keypad" (or something like that) keys.
On the VT52, these were blue, red and black.  On the VT100 PF1-PF4.
Later, PC keyboards, perhaps adopting IBM 3270 practice, sprouted
insert/delete/home/end/pageup/pagedown.  This "Delete" key (v.s. DEL)
is expected by PC users to delete forward.  It does not correspond to
a single ASCII character.  On my i386 system, it generates ^[[3~,
which is structurally similar to ANSI escape sequences for the
extended keypad.  (In emacs, it produces ^D, which means that it does
what people expect, although people like me (and I suspect Johnny)
never type it in emacs - real ^D is easier to type, and works on all
keyboards, pc or not.)

Keep in mind that when one uses a system remotely over ssh (no X11),
keycodes aren't (and shouldn't be) sent, so we really have to think
about coding into ASCII.  Aside from X11 being configured on i386 to
make the key-where-DEL-should-be send BS and have xterm have BS as
erase, things are in pretty good shape now.

-- 
        Greg Troxel <gdt@ir.bbn.com>