How to filter for unchanged attributes in diff/adiff?

[Kovoschiz]

Question: I know I can use compare(delta: to find differences. How can I query for no changes? I want to find objects that older author is the same as (eg target user created then modified the object again), or different from (target user modified object last changed by others) newer author separately. I tried using uid: / uid()== in different scoping. But can't get what I want. Don't understand the order much.
Or I can do this for specific tags. But I still don't know how. Must I do a difference of changed objects from the whole set somehow? Is it even possible?
(Should I ask this here, or in Overpass Turbo? Would be nice if you add the discussion section.)