To anyone interested, the basic algorithm I’ve used to format aui’s labels is visible here, under the July 29, 2011 section.

The results are that the string:

"This is an example of a [white|label] which makes use of a few things:\n\n-[special:newlineLink|Newlines]\n-[special:tagLink|Tags]\n-[special|Regions] (though you can't see them)\n-Generally a bunch of text!"

Renders like this:

The basic premise is that you add global ‘styles’, which are associated with tags (like “white” and “special” above).  You specify a ‘region’ when putting in one of these tags, which associates all the words in that region.  Later, this will be useful for adding things like hyperlinks and tooltips.  If you want to insert a region without using a style, you can do something “[:like|this]” (where “this” is in the “like” region, but uses the default style for the label).

Since the heights and widths of all the chunks of text are dynamically positioned, it should be pretty straightforward later to add things like embedded icons, if I were so inclined.  Neat!