As Yury noted previously: New code, and lines that are touched during re-factoring, should confirm to the current style guide.

Regarding going through all the existing code and updating the style:
That would be a very large, and in part non-trivial, undertaking. This is probably not considered important enough currently, given the time it would require.
Note that just adding missing braces would be an easy change, but adding strict equalities/inequalities everywhere will be more difficult. Given that the current code might rely on implicit type conversion, all the strict equality changes will need careful testing.