See http://beta.musicbrainz.org/artist/1bb206d8-316d-4bce-9731-e56cef40df58/aliases

渡辺麻友 is used in Japan.
渡边麻友 is used in PRC.
渡邊麻友 is used in Taiwan.

It would be very helpful if a list of countries appeared next to each artist credit, so we know in what kind of releases that artist credit is used in. This will help show obvious mistakes and in general be more useful.

The difference is shown in the "before" and "after" Paint mockups.