You're having some kind of brain fever and unfortunately reading my article while impaired.

Tolkien is commenting on reincarnation in the "Primary World." In his lingo this means the real world as humans experience it.

This is not concerning elves, as you falsely suggest.

When Tolkien writes that no one can "deny the possibility of reincarnation as a mode of existence prescribed for certain kinds of rational incarnate creatures"—he is saying that humans might reincarnate.