This feels like a bug or maybe it's a feature request but essentially it appears that when you merge tickets, the ticket you merged disappears.

Such as the links on the emails goes to a 404 page and when you search the ticket ID it can't be found.

It would be nice if the links redirected to the ticket it was merged into and when searching for the ticket ID it loaded the ticket it was merged into or at least provided a page that stated this ticket is merged into ticket #123.