As the title says, how do I disallow Iragana, Katakana and Kanji characters.As a European organisation we can't read/pronouce these characters so we want to force 'Anglo' characters.
Where? If it is not in s2M options, you maybe can find another WP plugin to do that.
On the registration form, which comes from the S2Member shortcode.
No way to do with s2M out of the box. Did you try other ways, like 3-th party plugins? If other ways don't works, maybe can do with custom code, but better you try easer ways first.
Haven't looked into options from 3rd party plugins.... I thought maybe it could be done with a filter for allowed characters or so maybe....