2008/3/6 3tx38k@bma.biglobe.ne.jp:
This message is a solicit of further consideration of Bugzilla topic #13065 which is WONTFIX as of now. Please read Bugzulla #13065 and this mail in detail. https://bugzilla.wikimedia.org/show_bug.cgi?id=13065
As I have responded on the bug, I suggest that the Japanese Wikipedia use a custom script to suppress browser enter handling for input. I gave a simple script that can be used as a basis to achieve that effect by anyone who knows a little JavaScript. I also suggest you file a bug with Firefox. This behavior will definitely not be changed in any way on our side for wikis that are in English, German, etc.