Perhaps the most distinguishing characteristic of HTML5 is that it specifies exactly what to do with tag soup. The rules are worth a glance at some time, just to see how rather absurdly complicated they are to do the job of picking up the pieces of who knows how many terabytes and petabytes of garbage HTML were generated before they were codified in an attempt to remain backwards compatible with the various browsers prior to that. And then you'll understand why I'm not going to even begin to attempt to answer your question about how browsers handle various tag combinations. Instead my point is only that, with HTML5, there is in fact a very concrete answer that is no longer up to the browsers trying to each individually spackle over the various and sundry gaps in the standards.

But honestly no answer to "what does the browser do with this sort of thing" fits into an HN comment anymore. I'm glad there's a standard, but there's a better branch of the multiverse where the specification of what to do with bad HTML was written from the beginning and is much, much simpler.