Triple ampersand already came up somewhere. I don't quite remember in what context but iirc they simplify to normal lvalue refs (at least in that context).
I think you're talking about perfect forwarding and reference collapsing rules [1, 2], introduced in C++11, but that is a bit different thing occurring only in a template instantiation context. Normally, you wouldn't see triple ampersands in sane C++ code, afaik.