I would propose a function that gives the id(s) of a linked record, or add that functionality to “lookup()”.
This would be helpful for checking if linked records in different fields to the same table are equal, without having to rely on the left-most field being unique in the other table.
Current workaround:
Make a formula field in the other table that just displays the id, then compare those via “lookup()”
But this feels kind of unnecessary.