bug#57728: 29.0.50; Emacs writes wrong glyph at the bottom-right corner of text terminals

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  57728@debbugs.gnu.org,  Akib Azmain Turja
>  <akib@disroot.org>
> Date: Mon, 12 Sep 2022 08:38:31 +0200
> 
> This is because 'write' deliberatly leaves the bottom-right corner alone
> if the terminal has "auto right margin" (autowrap).

But AFAIU, the bug actually shows that we somehow _do_ write there,
although the display engine assumes we don't.  Right?