Hey Kelheor,
So I extracted your mesh and the material, and imported it into a new version of the engine using 4.15.3. I had a hunch as to what it was that was causing the issue, and my assumptions were correct for the most part. In order to determine if this is a true AA issue I needed to isolate the mesh and use simple materials. Below are the results I got between the 4.15.3 and 4.16.1
Temporal AA - 4.15.3
Temporal AA - 4.16.1
As you can see they are nearly identical aside from slight camera angles being different. This issue comes down to the normals of the material being very small and very pronounced. All I did to negate some of this effect was to add a Mip Bias to the normals which softened the edges, but still produced the desired look.
Mip Bias 0.0
Mip Bias 2.0
Here you can see how modifying the Mip bias helps significantly reduce the ‘aliasing’ you are seeing on the mesh. There might be a bug here, but there is not enough concrete evidence to support a regression in the AA behavior using the assets provided or tests completed.
Let me know if you have further questions.
Thank you,
H