MSAA causes black aliased outline with Atmospheric Fog with Forward Shading enabled. This does not occur with TAA or FXAA. Also does not occur if there is a sky sphere present.
Found in 4.19 CL# 4033788, 4.20 CL# 4369336, 4.21 CL# 4404204
The cube will have a black aliased outline
No outline would be present
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-64564 in the post.