The language in 4.2.8 notes that "If no commas appear within the QQ TEMPLATE, ...". Perhaps this is too informal. After all (unquote foo) has no commas.
Additionally the language "Unpredictable behavior can result if any of the symbols quasiquote', unquote', or `unquote-splicing' appear in positions within a QQ TEMPLATE otherwise than as described above". O RLY? :) How unpredictable? ;)