Normal Flip Modifier I have 8 objects sharing the same mesh (linked duplicates) and I want half of them to have their normals flipped, so I am searching for a modifier that flips all the normals on an object before I set out to write my own.
The mesh is asymmetric, so I can't use a negative scale. The two normal directions need to be separate objects so I can export them to different files for render order reasons. I'd prefer not to have two meshes, as then I'd have to keep them in sync if I edit one.
One solution would be a Solidify Modifier.
All credits to @lemon for making it work.

Add Solidify Modifier
Set Normals &gt; Flip, and Mode &gt; Complex
Add Weld Modifier