Leeds is a special case that doesn't conform to the standards. Partly for historical reasons, and partly because "Leeds" is not a county and brackets don't seem appropriate. I happen to think that it looks better with a comma too, and would like to stick with it for now.
When I first started editing Leeds, the naming was a real mess and most of it was in the city of "Leeds". I've been slowly chipping away at the edges to limit "Leeds" to just the center(ish), but there's a long way to go yet. Haven't yet decided where to stop, but it'll probably be around where the inner motorway starts.
I've not used any particular set of borders for naming the old towns/districts, and I don't think it's necessary to get them perfect. Wikipedia is a reasonably useful for this, as is OS Open Data. You can see from the City layer what size areas I was working towards. Don't worry about gaps either, as Waze will happily report incidents 'between X and Y'.
Places like Rawdon and Otley can probably drop their Leeds suffix however, as they are reasonably separated from the megalopolis. Check uniqueness of town names at http://www.gazetteer.co.uk