Upcoming changes in registration process

I don't understand the interface when the requester also has made some translations, which is one case out of nine currently in Special:ManageTranslatorSandbox and specifically a translator to Hebrew.

• The first column is clear, it's the source text.
• The second column has a translation and a subtext with the language name: I can tell because it's the same string shown at top or I'd have no idea what עברית is.
• The third column contains "existing translations", with a message key as subtext.
  • In one of them, it seems to be the existing text of the message in the subtext, which (in the source language) is identical to another untranslated message, so the latter is probably what's being translated (but I have no way to know).
  • In another, the same, but there are no other messages with that English text so the translated message must be the same. Will the new translation overwrite the old if I accept the translator, or if not what will happen of it?
  • In the other two cases, the third column contains nothing but the subtext.

metalhead, are you able to answer the questions above? I still have no idea how this undocumented feature works.

I'm still interested in answers to my questions. In the meanwhile I'm trying to collect what's known about the feature in FAQ#How_do_I_register.3F.