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.
[1] http://thbecker.net/articles/rvalue_references/section_08.ht...
[2] https://en.cppreference.com/w/cpp/language/reference