Using accidentals with octaves
Currently, Musescore does not display accidentals at the octave (in a same voice)
Concerning the playback, this does not pose a problem with the natural, since the note to the lower octave is the same as the note above.
On the other hand, for the sharps and the flats, the difficulty appears since the accidental to the octave is not added by default. And so playback is deficient - you have to manually add an accidental. Anyway, what is shown can easily admit to ambiguity.
Elaine Gould (Behind Bars), p.78-79 seems clear on the fact that "each additional octave requires a further accidental"
So, MuseScore displays and plays this: altérations.mscz
Sibelius (7.5) has a different behavior: the program displays a natural, by default, and it continues to do the same for sharps and flats. In a way, you're warned.
And for Finale (2012) : again a different behavior (but for the playback, it's ok, and for the display probably too, except for the natural, less expected?):
So it does not display the natural (as MuseScore), but it shows a second sharp and a second flat to the octave.
Any thougths about the best expected behavior for MuseScore in this use case?