R5RS interpreters need not apply?

[jar@cs.cornell.edu (Jonathan Rees)]

   Date: Tue, 6 Apr 93 14:56:29 -0400
   From: "Aubrey Jaffer" <jaffer@martigny.ai.mit.edu>

   Are the considerations of scheme interpreters no longer relevant to
   the authors?  R4RS was implementable in a small, fast program; The
   macro requirement of R5RS is not.

Sorry, I'm not convinced of this.