I don't know why this is happening is it because of the light? Something new with how lights/shadows work in 2.8? This happend on the 2.8 Candidate 1 and 2. I have plane with emission as light in this project. You can clearly see that faces are different. This never happend to me.
This is cube mesh with verteces merged in center to create a blade.
I tried flipping normals, playing with light and the object but nothing worked.
EDIT After playing with light some more I got to the point on last picute. I just upped the strength of the lights. Didn't really help you can just see it less.