In section 15.10.2.6, the assertion \b is currently defined for ASCII only, since the standard defines "The abstract operation IsWordChar" returning true for only 63 ASCII characters.
I believe it should instead be phrased as "The abstract operation IsWordChar returns true if and only if CharacterClassEscape w returns true".
The reason I'm requesting this change is that I'm a C++ developer, and the C++11 standard points to ECMA-262 for Regular Expression syntax. For Unicode strings, \w matches all Unicode alphanumeric characters, whereas \b only matches ASCII characters. I am using the workaround of changing \b into (?!\w), and it works, but it's very confusing to have \w to match one set of characters and \b work with a different set.
Substantive changes should go through the proposal process defined here: https://github.com/tc39/ecma262/blob/master/CONTRIBUTING.md.