I've noticed that papers remain in the "unsorted" filter even when added to a shared folder. I'm mainly adding papers to shared folders for use by my team (and not using private folders at all). Is this expected behavior?
This is the expected behavior - shared folders are entirely independent of the organization of papers in your library and the "Unsorted" filter refers to the latter.
We may look into changing this behavior if more people find it odd or problematic,