R1:53b9acfb7d58

Test for "CAN_INTERACT" on comment edits in a way that survives objects which only implement "CAN_VIEW"

Summary:
Ref T13289. See D20551. In D20551, I implemented some "CAN_INTERACT" checks against certain edits, but these checks end up testing "CAN_INTERACT" against objects like Conpherence threads which do not support a distinct "CAN_INTERACT" permission. I misrembered how the "CAN_INTERACT" fallback to "CAN_VIEW" actually works: it's not fully automatic, and needs some explicit "interact, or view if…