Oh, that stuff gets pumped out as valid, unforunately we can't expect users to understand proper nesting.
[b][i]Test[/b][/i] results in a validation error . It's the same for every other forum software, as we'd require a complex token tree to even come close to compensating for that stuff. I know CC had that before, but the code never got checked in.
That and the issue with people doing
[i][quote]test[/quote][/i], putting block level elements inside of inline elements.
