Regarding harmony added to the right hand notes when playing a chord, The idea behind this is to add extra notes to a single right hand note. It is not meant for you play more 2 or 3 notes because the harmony feature is bound to get confused, if you are playing 2 or 3 notes why have the harmony on at all.
Of my previous keyboards Korg, Roland & Yamaha, the Yamaha gives a cleaner harmony to a single right hand note.

Graham UK

Graham,
you are correct and that is why I never noticed it on the X1. However, when playing quickly using piano voices, it is possible to hit two notes at the same time which then makes the harmony sound sloppy because of the note off sound.
George Kaye
Kaye's Music Scene
Reseda, California

George:
Thanks for you invaluable help on this issue. I am glad that Italy finaly recognized the problem on their keyboards and will be doing something about it soon. Maybe there is an XD9 for me in the future after all, or even perhaps another X1. You are truly a "hands on" person and we are lucky to have you in this forum.
Graham:
I agree, Yamaha does this function the best of all keyboards I know of. As to the problem with the Solton/Ketron boards, the situation presents itself when playing single notes (not multiple as you mention) only they have to be played at a moderate speed and in succession for the condition to manifest itself.
Regards
Mario