"Phonto" comes from its connection to "Uso." Hasegawa intended there to be a deliberate dichotomy between "uso" (meaning "lie") and "honto" (suggesting "real" or "truth"). This duality extends beyond mere wordplay since Phonto was designed as Uso's perfect antithesis, with every aspect of his character serving as a mirror opposite, from his narrative role and combat capabilities down to his family dynamics. Having the spelling Font loses this entirely. Granted, this fact wasn't apparent until volume three of Ghost came out, so... go figure.