UglyUncle, I understand your decision to stop submitting. I almost did the same a couple of years ago. I gather there is already concern about the declining number of entries, so The Listener can ill-afford to lose more. I agree with you about the grape clue. I thought you might also comment on the non-Ximenean god-daughter clue, which seemed nonsensical to me.
It’s a pity that an otherwise good puzzle has been spoiled by uncertainties in the endgame. I think the option advocated by UglyUncle and maybe others is probably not the intended one. My main reason is that a very similar recent puzzle by the same setter in another publication required non-alphanumeric resolutions. That’s not a logical reason, I admit, but I’ve been caught out before submitting a solution that the setter did not intend. Even then, there are ambiguities. For instance, a consistent depiction from Wikipedia does not match that of another ‘scientific’ site in several respects.
A slightly differently worded hidden message could have made it absolutely clear which of two forms of representation was required, and a preamble assurance that some latitude would be permitted would have avoided all this angst.