User blog comment:RottenBlock/System 3 Compilation, Part 5/@comment-44256294-20200122141129/@comment-31720212-20200122224847

Thanks, you've probably nailed it, then. It's funny to think that column mode and regular mode functionally do the same thing with this mask in play, but if it's for something like that, I can understand it. TTSys also responds to operating system checks (Y 254) by replying that you're on the PC-98 except in a few instances, so it would make sense that its defaults are set in that direction! The mask must have been disabled for other platforms, something TODO missed when he created the new interpreter.

Thanks, I wouldn't have worked that out without your insight!