Hang on - if nobody seems to use {{{{{ }}}}} then why is this what Creole chose? Why not the more standard {{{[[ ]]}}} notation?
-- Nicolas Wu, 11 Feb 2008

Because {{{[[ ]]}}} is already taken for links, and it's indeed the most standard notation for them, apart from CamelCase. Using teh same markup for both just doesn't work -- some wikis treat images as normal pages, others as attachaments, you often want to have the ability to choose whether to display the image or to link to it. The {{{{{ }}}}} markup is nicely consistent with {{{[[ ]]}}} and doesn't collide with most existing markups (the mediawiki templates can be resolved, I think there was a wiki using it for monospace too, but it had a lot of other strange rules). Besides, MoinMoin now uses {{{{{ }}}}} for images and page transclusion too.
-- RadomirDopieralski, 11 Feb 2008

Thanks for the answer. So taking this abstraction further, would we say that {{{[[ ]]}}} always takes us to another page in the wiki, or to an external link, whereas {{{{{ }}}}} will try to embed the content directly in to the page? For example, we might want to embed a flash video, plug in some raw text, or even directly insert the content of another wiki (as far as I know this isn't done, but I'm wondering if it might be a useful extension).
-- Nicolas Wu, 12 Feb 2008