For posterity: I did the following to resolve the problem:
To prevent the xconsole from appearing at the login prompt, I commented the following lines out of /etc/X11/xdm/Xresources:
Code:
!XConsole.text.geometry: 480x130
!XConsole.verbose: true
!XConsole*iconic: true
!XConsole*font: fixed
The '!' character is used for comments, apparently.
To prevent the xconsole from appearing after login, I commented the following lines out of /etc/X11/xdm/xdm-config:
Code:
! DisplayManager._0.setup: /usr/lib/X11/xdm/Xsetup_0
! DisplayManager._0.startup: /usr/lib/X11/xdm/GiveConsole
! DisplayManager._0.reset: /usr/lib/X11/xdm/TakeConsole
It is a little odd that I had to do that, since the files referenced (Xsetup_0, GiveConsole, TakeConsole) don't actually exist... but, hey, whatever works.