I've watched that video on the Whistleblower a few times now and I'm actually convinced that Suarez dived. The first angle showed the dive perfectly and I didn't actually believe it at first, when I watched it again it was pretty blatant and I'm sure there would have been a caution instead for Suarez if the referee had been lucky enough to have the angle the camera did.
I get the impression that the referee thought that was the case too and it was being looked for through the slightest of contact. It'd explain the caution for Richardson, because he had that element of doubt over what Suarez did. A sending off would have been very, very harsh in those circumstances because of the way Suarez went down.
I'm sure Liverpool fans will castigate for this one, but ask yourselves this: Suarez, for no reason, flicks his feet up when any contact would have been in his back. Why on earth would he actually do that? Also, consider this: would you have been happy to see one of your defence go off for such a blatant dive?