- first available loadable-font slot number (e.g. 43)
- result of previous "select font" request (0 = success)
- current video mode flags (e.g. high-intensity background)
- current emulation mode flags (e.g. cursor visible, doorway mode)

These are to aid the server (BBS) in making better use of advanced features,
namely alternative/loadable fonts and high-intensity background colors (aka iCE
colors). Being able to detect when these features are supported and working as
intended is vital in providing a smooth/automated BBS experience which is
automatically enhanced, when possible (supported by the client) and does not
interfere with legacy (non-enhanced client) users.
Even better would be a command that tells the server:
if the server were to attempt a request 'X', it would likely work.
Instead, we have to try request 'X' and then query the device attributes to
find out if it actually worked, which is better than nothing (or asking the
poor user to tell the BBS whether it worked or not).