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I can't support this proposal.

I believe that the correct fix is for wording to be added that explains
that *TERMINAL-IO* might be a bidirectional stream which directs input
 from and to a virtual and not necessarily a physical terminal. As such,
*TERMINAL-IO* should properly be initialized to
If it were, then *STANDARD-INPUT* and *STANDARD-OUTPUT* would behave
correctly with no relaxation of the requirements on their initial values.

I think it is important that *STANDARD-INPUT*, *STANDARD-OUTPUT*, etc.
be defined to be bound to synonym streams initially. Here are some reasons:

 * It may be important to the programmer to recover the value of this
   virtual terminal. There is already a restriction on binding
   *TERMINAL-IO* in Common Lisp, so the virtual terminal will always
   be accessible from *TERMINAL-IO*. If the virtual terminal were in
   *STANDARD-INPUT* and *STANDARD-OUTPUT*, the user might bind himself
   into a corner where he could no longer recover the value of the
   virtual terminal.

 * I think the initial I/O pairing should be available as a unit rather
   than in two different places.

 * If there is no physical console, the value of *TERMINAL-IO* will
   have garbage. There is no reason that input/output from/to programs to
   *TERMINAL-IO* should fail just because an alternate input or output
   stream was provided. You cannot make *TERMINAL-IO* indirect via synonym
   stream to *STANDARD-INPUT*,etc. without risking complete disaster.
   If it did, the user might do:
   and get a circular synonym stream. In order to make sure that programs
   can portably use synonym streams at all, it is extremely important that
   the directionality of synonym streams be well-defined (ie, from 
   *STANDARD-INPUT* to *TERMINAL-IO* and not vice versa) and that there be
   a known bottoming out point, *TERMINAL-IO*, which cannot be a synonym
   stream to anything the user can get his hands on.