See PHI1209. When a task is in "Hard Lock" mode, it's still possible to apply some changes to it. Notably:
- You can subscribe/unsubscribe.
- You can mention it on another object.
- You can add a relationship from some other object to it (e.g., select it as a "Parent Task" for some other task).
Currently, these types of edits will show a "Lock Overridden" timeline emblem icon. However, they should not: you didn't override a lock to make these changes, they just bypass locks.
For now, special case these cases (self subscribe/unsubscribe + inverse edge edits) so they don't get the little icon, since I think this list is exhaustive today.
Some day we should modularize this, but we'd need code like this anyway (since TYPE_SUBSCRIBE is not modular yet), and this seems unlikely to cause problems even if it's a bit rough.