And if we're talking about SMS... 160 characters covers the 7-bit GSM alphabet. Once you enter something outside that (e.g. lower-case greek) you end up in a regional 8-bit encoding and you only get 140 characters. Enter something outside of that (e.g. asian languages) and you're into UTF-16 and you may only have 70 characters (and now you get to explain to your users why emoji with skin tone modifiers count as 4 "letters").