The brackify function returns the closure [+ openb _ closeb]. The [... _ ...] notation means "construct an anonymous function of one argument, _"; it's the same as (fn (_) (... _ ...)). Thus, (brackify "(" ")") returns a function of one argument which, when called, surrounds its text with "()"; the text given is "adm".
The downvote buttons have been there for quite a while for me---you seem to have just broken 100 karma, so maybe it's because of that?
