Apply suggestions from code review

Co-authored-by: Ralf Jung <post@ralfj.de>

Author: joshlf

src/types/pointer.md

@@ -56,6 +56,10 @@ Despite pointers and references being similar to `usize`s in the machine code em
 the semantics of transmuting a reference or pointer type to a non-pointer type is currently undecided.
 Thus, it may not be valid to transmute a pointer or reference type, `P`, to a `[u8; size_of::<P>()]`.
 
+For thin raw pointers (i.e., for `<T as Pointee>::Metadata == ()` and `P = *const T` or `P = *mut T`),
+the inverse direction (transmuting from an integer or array of integers to `P`) is always valid.
+However, the pointer produced via such a transmutation may not be dereferenced (not even if `T` has size zero).
+
 [`core::ptr::addr_of!`]: ../../core/ptr/macro.addr_of.html
 [`core::ptr::addr_of_mut!`]: ../../core/ptr/macro.addr_of_mut.html
 [Interior mutability]: ../interior-mutability.md