View the attachment "msg" in a frame. Split into 2 windows. In the
lower window, click and hold on the scrollbar down arrow, so that text
starts scrolling up. Keep going until the message from
email@example.com gets to the modeline for the upper window. As
you keep scrolling, notice how that line is written over the top of
the modeline, rather than being clipped by it. See the attachment
Reproducible with -vanilla. Reproducible with 3D modelines disabled.