The difference between traditional and simplified Chinese characters is more than simply different fonts. Part of the difficulty is that some simplified characters map to multiple traditional characters, which means that converting from one to the other may be lossy. There's also the Japanese equivalent of simplified characters (shinjitai), many of which differ from their Chinese counterparts, as well as characters that were invented in Japan and may or may not have Chinese equivalents (kokuji).
Simplified and traditional characters have different unicode codepoints. Japanese and mainland simplifications have different codepoints when they differ, and Japanese-only characters of course have their own codepoints.
The argument is about characters like 冷. It is given a single codepoint, but Chinese typefaces draw the bottommost stroke diagonally, and Japanese typefaces tend to draw it vertically. (When writing it by hand, both versions are acceptable in Japanese also, http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q105... )
The Cyrillic R (looks like P) and and Greek Roh (also looks like P) and the Latin P are not unified either. Although I think unifying some Greek and Cyrillic letters would have made sense.
