I think this situation is not that simple. There are multiple things in play here:
1. Cut lines
2. Uncut lines
3. Fills of cut surfaces
4. Fills of uncut surfaces
5. Vectorial hatches on uncut surfaces
6. Hidden lines
Currently, hidden lines are drawn in front of all other lines and fills.
If hidden lines were drawn behind all these, then hidden lines would not be visible behind any fills.
I think the way this should work best is hidden lines should be in front of all fills, but behind all other lines. I think this would be a more complex thing to achieve technologically, because you would have to separate the drawing of fills and lines (or maybe it is relatively simple, I am just guessing).
So I would say this is more a feature than a bug, but a feature that could be implemented more intelligently.
So I will forward this to GRAPHISOFT as a wish.
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