> Why? It may keep a polygon island from getting disconnected or necking down below DRC parameters. It may allow for an extra trace between pins. If the pin is intersected by a 45 degree line, it prevents notches from being cut out of the clearance:
http://www.delorie.com/pcb/notches.html It does get ugly when you have a row of square SMD pads, though. You end up with lots of little triangles cutting into an otherwise straight clearance edge. I think, if we decided to use rounded-corner clearances, we'd need to be intelligent about rows of pads with overlapping clearances, and join them into a single rounded-corner clearance that covered them all. That might speed up display and reduce gerber file sizes, too, even if we implemented it for square-corner clearances.
