If the HTML 5 standard has a tag which requires browsers to do X and they all do X except one browser lets say Internet Explorer does Y what is the solution?
a) update the standard and force all other compliant browsers to do Y when they encounter and .
OR
b) demand the broken browser update their implementation so that when it encounters an tag it does X not Y.
If the most widespread implementation does it one way, then it becomes standard. Happened with IE bugs, happens these days with Safari and Chrome bugs.
Public does NOT GIVE A DAMN about geeky correctness. If a page fails on FireFox but works with IE, users will accuse FireFox/Chrome and stick with IE. They did. For years. So FireFox and Chrome supported Quirks mode, and still do.
If MtGox fails because of bitcoin technical reasons, well, bitcoin gets bad press.
Either this is taken as an opportunity, or it will be taken as a blow, that's all.