I don't know why it has died.
Workarounds:

F8, then Alt+Enter.
In Opera 21 you can middle-click the Reload toolbar button, it kinda works as clone tab.

Im trying to middle click the relad button in O21, but it just acts as normal left-click Any idea why?

In Opera 12 was one more mouse gesture: Duplication of current webpage tab (by holding right mouse button and moving down and up).

In newer versions it has just vanished (and the combination does not do anything at all...)

Does anyone has idea why? (Did no one use it??)

I am quite disappointed that its missing. Is it just me?