To be fair, that actually isn't valid UTF-8 - the leading byte has no zero bit. The largest valid UTF-8 encoding is FE BF BF BF BF BF BF, with value U+F'FFFF'FF

To be fair, that actually isn't valid UTF-8 - the leading byte has no zero bit. The largest valid UTF-8 encoding is FE BF BF BF BF BF BF, with value U+F'FFFF'FFFF. (In fact, the original specification only listed up to FD BF BF BF BF BF (U+7FFF'FFFF).) Furthermore, even if you assume a implied zero bit at position -1, that would only be FF BF BF BF BF BF BF BF, with value U+3FF'FFFF'FFFF. Also 7FFF'FFFF'FFFF'FFFF is only 63 bits - fer chrissakes son, learn to count.