When a differential revision is merged the lint and unit test results on the differential view are not displayed anymore but this text is displayed:
Automatic diff as part of commit; lint not applicable. Automatic diff as part of commit; unit tests not applicable.
There is no way to view the results of the last diff before the merge even if you switch to an older diff id. Not sure if this data is deleted but i don't think so.
So my expected behavior would be to show the related linter and unit test results when switching to a specific patch id (http://foo.bar/D1379?id=3989).