TracDuplicates is a plugin for trac that will allow to dupe a bug against another generating "Marked" comments like bugzilla does in both affected bugs.
Working Trac 0.10 (tested with 0.10.4)
Add the Workflow
[ticket] workflow = ConfigurableTicketWorkflow,DuplicatesWorkflow
Add Workflow items
[ticket-workflow] duplicate = * -> closed duplicate.operations = set_duplicate duplicate.name = Close as duplicate of