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AFAIK there isn’t a list of the Post Process effects which are disabled in split-screen, but I know motion blur and TAA are (and probably bloom and lens flares). It is disabled because of issues that arise from power of two down sampling of the target that contains multiple screens.
I have entered a Feature Request for an option to Re-enable Post Process effects for splitscreen which can be tracked here. Currently the only way to re-enable these effects is by modifying the source code.