At the moment the worst problem I'm having is bright pixels caused by MSAA. I think it's related to triangles that are very oblique, then for some reason the GPU produces occasional super bright pixels that are far brighter than any vertex colour or texture colour.
Previously these have appeared as single white pixels so were not too disturbing, though they have been showing up more in night scenes. This is regardless of SDR / HDR mode, and they appear even with plain ambient diffuse lighting with direct lighting switched off. In SDR it renders straight to the backbuffer, so it's not related to render target textures. And it still happens if I switch off AF. The only thing that removes the bright pixels is switching off MSAA.
But now with bloom enabled the bright pixels have become quite a problem. They can be brighter than the sun and I'm getting quite a few of them every lap. The bloom causes them to be very noticeable.