I really appreaciated the whole rejection of the "hero" ideal of Dune Messiah, and the effort FH put into making the culture and society of the empire even deeper than in the first book.
For this reason, this detail immediately bugged me and I can't think of a good explanation for it.
The whole fremen society is build on water preservation, with striking details like ''giving moisture to the dead'' which really drive in the concept.
So, why is it that fremen who become blind should walk off in the desert to die? I understand the pragmatic idea that they cannot afford to take care of them, but is it not true that
''A man's flesh is his own; the water belongs to the tribe''.
This seems like a huge waste of water! Why not letting them ''fall on their knife'' honorably, then take their water?
I get it it's necessary for the plot, but I was wondering if anyone thought of any way to justify it water-wise.