I use QuestyCaptch (it is in ConfirmEdit extension) to fight spam.
I use CSS in wiki's Common.css page to make the question more
noticeable, because otherwise it just shows up in normal text which is
not obvious and very easy to overlook.
I am successfully styling the QuestyCaptcha question for page edits
that add URLs with this in Common.css:
/* ConfirmEdit QuestyCaptcha, on add URL in edit