I was planning to add a new table TA only writable by user A, with a foreign key reference with ON DELETE CASCADE to another table TB only writable by user B. My hope was that user B would still be allowed to delete rows in TB and cause cascading deletions in table TA, and some manual investigation makes it seem like that is the implemented semantics.
Am I correct that (a) no permissions are needed here and (b) this is undocumented and (c) it would be helpful to document this, probably in the CREATE TABLE docs? Happy to write a patch if so.