The gj thread
got me thinking about how serious of an issue is the overlap of different letters. I imagine this is a wide topic - it may cause issues on some systems, for all I know. I can immediately think of one case that is not insignificant: letters made for outdoor advertising. If there is a collision, a designer would have to clean it up and weld the text aesthetically before it gets... um, welded in metal. If this has to happen every time the font is used, this could lead to dropping it in favor of more composed fonts.
(This would probably be a good time to go on a tangent and ask if FontLab can measure Bezier length in cm.
Corel had an option for that in the past, but I haven't used in ages. FWIK, Adobe Illustrator has to use a plug-in, not to mention the AI canvas is restricted in size.)