Drop a noisy reminder

- compare_vf is invoked for implementation of transitive closure, and
  there I don't think we care what the frame contents are.  Transitive
  closure has a scope of its own, and frame contents don't leak out
  anyway.  So the only thing that we care about is actual stack
  contents.  It would actually be an error (or at least not useful) to
  produce two indentical stacks just because inside the closure, their
  stack frames contained different values.