SUBTYPEP-TOO-VAGUE, version 3

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

SUBTYPEP-TOO-VAGUE:CLARIFY looks good to me.

Since some implementations might use the prohibited words internally
in implementation of built-in types, for example,

  (deftype simple-array (&optional element-type dimensions)
    `(and (array ,element-type ,dimensions)
	  (satisfies simple-array-p)))

I think you need to say explicitly that subtypep cannot return a second
value of nil when both arguments involve only the words in Table 4-1, or
names of defstruct- or defclass-defined types, or user-defined deftypes
that expand into only those words and/or names.

I think you're right that the rules for comparing the various type
specifiers could usefully be spelled out in detail.  Maybe some ad hoc
committee to do just that should be set up?