Backquote, comma, and comma-at are reader macros that expand into quasiquote, unquote, and unquote-splicing, respectively. So your example expands to
(quasiquote (a b (unquote-splicing args) (unquote x)))
If you allow unquoting within quote, how do you tell the difference between an evaluated (unquote x) form and a literal (unquote x)? You might want the latter if, for example, you have a macro that returns another macro with unquoting.
