I, one of the 3 reviewers in the German translation project, realized that one half is formal and the other half is informal!
Should we use formal or informal?
I guess it is up to you as long as users are comfortable.
In Turkish, I changed all informal expressions to formal ones... maybe except in ACP... in the admin panel, I am ok with any translation as long as it is meaningful, and I personally prefer to use ACP in English, since terms are more understandable to me.
I guess the German version would be using "formal Sie" rather than "informal du"... English does not have this distinction, but Turkish and German have...