Hi Nicolas
Yes we had problems with the answer. The things we had to change where not working, the support in Japanese was not really helpful as the way to do it was not explained well and my Japanese partner did not really understand where and what to change. I have to tell that we have no php. knowledge and we need the exact way to do it. If the steps are not explained well then we can't do it.
I'm always happy with the English support that's why I thought it will be easier for us to ask here and get the right answers.
Anyway, I just found a way to make it work today, without changing any of your mails.
I switched the Last name and First name in the registration form (custom fields), changed the order in the address_template (views) and override the Last name and First name in the language file.
This way the Last name and First name shows incorrect in the Customer database, but shows correctly in every mail and Invoice.
Best regards
Raphael