Looks like it creates some additional space, Paul. I don’t care what anyone says, Vincent Connare knows what’s up and here’s a little something he says about it (notice the illustration and the UC configuration—either serious kerning or a composite glyph): http://www.microsoft.com/typography/developers/fdsspec/diacritics.htm

More about Catalan ldot / Ldot can be found here:

http://diacritics.typo.cz (Dot Accent)

There is also a link to a PDF about Catalan ortography.