Claude Paroz suggests: Rosetta should "...highlight the last upstream translation in the suggestions (using the same green colour as in status bars would be nice). Add a button "Revert to upstream" that put back the original upstream translation in place. It's important to note that manually copying the upstream translation has not the same effect, because if a modification is done upstream later, it won't automatically replace the manually added string.
"Alternatively, you could prevent adding this new button if the system automatically recognizes that when I manually add a string identical to upstream one, the string resynchronizes with upstream, that is the 'Translated by' field shows upstream data (translator and date) and the string is marked unchanged in Rosetta (green colour)."
I strongly support this idea. It would solve a lot of problems with upstream.