8.7.24138.15431, 2024-05-17
As stated on AutoCAD 2025 Help | To Work with Layers | Autodesk, the vertical bar ( | ) is not allowed in layer names. However, Rhino exports them verbatim to DWG and DXF, while converting other non-allowed characters to underscores. Autodesk Fusion refuses to import DXFs with these non-allowed characters.
Layer name in Rhino
< > / \ " ; ? * | = `
Layer name in DXF export (Acad 2000 - 2018)
_ _ _ _ _ _ _ _ | _ _
I didn’t include ( : ) since Rhino removes them in a .3dm save.