I'd say an alias. This doesn't strike me as a distinction we need to preserve.
Posted under General
+1 for alias. Having separate tags for one exclamation mark and two is just tag overkill. What's next, tagging post #627117 with !!! and post #624880 with !!!!? (And the tags' usage doesn't even support a distinction, see post #710087 and post #711585 which contain "!!" but are tagged as !)
In my opinion, there should be no implication or alias on this one (I think I've added ! to !! posts in the pasts, so I was thinking implication at first, but maybe worth keeping them separate) !! should be used in any situation where there's two exclamation points next to each other, regardless of how many (using !!! and !!!! is definitely unnecessary).
I'm opposed to letting them stay separate, myself. Unlike the usage of !? versus ! and ? separately, !? constitutes its own reaction (usually shock or surprise) separate from the other two.
On the other hand, the only difference between !, !!, !!!, and so on is the degree of exaggeration.
+1 to aliasing it.