+>>> `[^\s()]+` is a character class matching all characters not spaces or
+>>> parens. Since the pervious terminals in the regexp consume most
+>>> occurances of an open paren or close paren, it's unlikely for one to
+>>> get through to that part of the regexp. For example, "foo()" will be
+>>> matched by the command matcher; "(foo)" will be matched by the open
+>>> paren literal terminal. "foo(" and "foo)" can get through to the
+>>> end, and would be matched as a page name, if it didn't exclude parens.
+>>>
+>>> So why exclude them? Well, consider "foo and(bar and baz)". We don't
+>>> want it to match "and(" as a page name!
+>>>
+>>> Escaping the parens in the character class actually changes nothing; the
+>>> changed character class still matches all characters not spaces or
+>>> parens. (Try it!).
+>>>
+>>> Re commands containing '(', I don't really see any reason not to
+>>> allow that, unless it breaks something. --[[Joey]]
+