System Information
Operating system: Windows 10 x64
Graphics card: Nvidia 980

Blender Version
Broken: 2018-11-29 15:57, 26d5a3625ed, blender2.8

Short description of error
EdgeSplit Modifier doesn't produce separate faces if Split Angle is set to 0 and the mesh (or part of) is a flat object.

For example: Create a grid object with subdivisions greater than 1 and add an EdgeSplit modifier with Split Angle set to 0. Splitting the mesh now to loose parts or working with a Smooth modifier shows that the modifier didn't produce the desired effect.