Earlier, Will wrote:

   On my reading of the R6RS and R7RS, it is probably legal for a
   literal to be followed by an ellipsis in patterns.

and Marc wrote that it "should be regarded an error if a literal is
followed by ellipses in a pattern", and asked "what would be the
meaning of this?"

I've always thought this was unambiguously allowed, and had an obvious
meaning.  The spec says that for any valid pattern P, the pattern (P
...) is also a valid pattern, so I'm not seeing the problem.