Chapter "The basic modes" section "Autodetecting the direction" says "UAX #9 doesn’t specify an exact algorithm for autodetecting the paragraph direction." That's not quite correct; it does, it just adds as an exception "Whenever a higher-level protocol specifies the paragraph level, rules P2 and P3 may be overridden."
In chapter "The escape sequences" section "Other output modes" presents "a few weak arguments for picking the disabled state as the default". However, UBA rules P2 and P3, i.e. autodetection, is clearly the default suggested by UBA. I think this is a strong point to define autodection to be enabled by default.
In any case, I think this is an essential parameter to influence the actual handling, so it should not be hidden under "Other output modes" in the description; also as I've suggested elsewhere I think a DEC private mode does not properly reflect the importance of this setting.
In the test file, please add an explicit escape to disable autodetection initially as test evaluation depends on this setting.