Fix LWG 2874.
Nitpick: You've got the wrong LWG number in your commit message.
Also, can you please mark the LWG issue as complete in the docs?
You are eagerly instantiating all templates here, and I don't think that's what you want. For example, you'll instantiate __well_formed_delete_op<_Yp*> even when is_array<_Tp>::value is true.
STD_TEST_VERSION doesn't exist, it's TEST_STD_VER.
To catch these sorts of errors, it can be good to add tests and witness their failure before actually fixing them.