Please note that this does does not require invasive the modification of
the syntax of the language as alternative scoping semantics would; this
specification only extends the definition of comment, and defines previously
ambiguous reader-quote/etc. syntax/semantics.

> And finally, slightly simpler:
>
>  <comment> -> <datum-comment> | <empty-quote> | ; <all-chars-to-eol>
>
>  <datum-comment> -> #; <datum-or-comment>
>
>  <datum-or-comment> -> <datum> | <comment-or-empty>
>
>  <comment-or-empty> -> <datum-comment> | <empty-quote> | <empty>
>
>  <empty-quote> -> '  <comment-or-empty>
>                 | `  <comment-or-empty>
>                 | ,  <comment-or-empty>
>                 | @, <comment-or-empty>