That's not a real issue. I can understand this may bite some people that don't read the docs or don't understand encoding, but it's more misinformation than a technical problem.

UTF-8 is variable length anywhere, not just inside mysql. If you don't want this behavior, you can either use UCS-2 or UTF-32. UTF-16 and UTF-8 are variable length encodings, period.

Most databases that have use char length for unicode actually work with UCS-2, and use 2 bytes per char, like MS SQL Server.