I've noticed some pending suggestion and was about to start committing a few I could clearly validate since they didn't have any Japanese equivalent yet, but then I thought this should also be subject for discussion.
So first, I apologize for committing 8 strings in my eagerness to be useful and started this wiki page in order to exchange ideas on the subject.
I propose the following:
For any member that has commit access (admin) I suggest we could freely accept any suggestion that provides a decent translation to any untranslated string. What is a "decent" translation is left to the ability of the admin evaluating the suggestion and I personally thrust every member to do to the best of his judgment. Of course, in the case of doubt, leaving the suggestion as is for another admin to review is advisable.
We also need other rules, so please use this wiki page to add your ideas and edit freely.
I will try to provide Japanese later and would be quite happy if anyone beats me to it.