We had several regularly-invoked model instance comparisons in the

product that could result in unwanted database queries. These were

usually found in accessibility checks, comparing if a requesting user

matches the user owning an object.
To reduce overhead, we now compare the IDs, which is faster even if the

instances were already loaded. This cuts down on a number of queries in

common usage.
Test coverage for these checks have been improved, with many

accessibility checks that were previously covered implicitly through

other test suites now having explicit test coverage.
There's also a fix for a bad permission name, which impacted the tests.

The can_edit_status permission for StatusUpdate needed to be

change_statusupdate.

Unit tests pass.