When I select a failed job and one of the bug suggestions for that failure is crossed out because it is resolved - duplicate, it would be nice to show what bug it is a duplicate of in the tooltip (instead of just "duplicate"). I believe that number is surfaced in the api as "dupe_of". If dupe_of is not null, it should be the id of the bug that this bug was duped to.
I think Treeherder shouldn't try to fix up bad input data. The duped-to bug should be updated to have the correct summary / keyword moved over etc.