... I am particularly offended by the message Query OK, when it clearly isn't.

I agree with you that this is questionable default behaviour, but at least it's documented, and (as of version 5.0.2) it seems you can enable a "strict mode" to have it error out:

"If you assign a value to a CHAR or VARCHAR column that exceeds the column's maximum length, the value is truncated to fit. If the truncated characters are not spaces, a warning is generated. For truncation of non-space characters, you can cause an error to occur (rather than a warning) and suppress insertion of the value by using strict SQL mode. See Section 5.2.6, "SQL Modes"."