The traditional cedilla looks very uncomfortable on many realist sans-serif fonts since it looks quite calligraphic and slender. So some modernists (including Adrian Frutiger) preferred a beefier comma or accent-like design. Left: Helvetica with standard cedilla, right: Akzidenz-Grotesk Book with its modernist cedilla. URW Grotesk (not shown) has an interesting compromise between the two styles.