Brian Kelly: I was, though, also very shocked that a validator for such a widely deployed standard (RSS 1.0) had such bugs
There is no question that RSS 1.0 is widely deployed. RSS 1.0 has a minimal core. The validation for that core is pretty solid.
Not all RSS 1.0 modules, however, are equally well deployed (or particularly well defined, for that matter). I can’t honestly say that there aren’t bugs in lesser used extensions, in fact, I’m positively sure that there are.
The only thing I can say is: test cases welcome. For example: here is the one and only testcase at the moment for the taxonomy module.