This is mostly fine if only done for ambiguous letters and if the understanding is that it is done to reduce ambiguity. There is a contingent of people who painstakingly spell out every letter with a phonetic from their own system and it requires the listener to do a lot more decoding to the point of actually increasing ambiguity. "My name is Michelle that's M/N as in Nail/Mail! I as in Icecream! ..." Nichelle is confused about why we use words to spell out certain letters.