Comments below come with the usual caveat that I am not a ref, rather just someone who appreciates that the analysis of decisions I didn't understand here is several magnitudes better than on television.
Re: May's yellow card. My reaction in real time was that Fickou had fallen awkwardly in trying to spin out of May's tackle, but that it wasn't a penalty on May's part. On seeing the slow motion, I can understand how you can tick off all the requisite requirements for a penalty - May is clearly holding onto a leg which comes past the horizontal, and there is arguably some lifting motion to get it there - and once you're satisfied on that part, a card clearly follows (indeed, since Fickou seemed to land part-shoulder / a lot of face, then it could easily have been a lot worse).
My issue in some ways is that to me it doesn't feel like the sort of incident that was intended to be caught by the dangerous tackle laws / directives etc, which I always thought was aimed at preventing something like the (in)famous Warburton-on-Clerc tackle.
Had AG ruled that the primary cause of Fickou's leg going above the horizontal and his landing awkwardly was his attempt to spin out of the tackle, and that any lifting action by May was incidental and not a cause of this, would the wise sages on here be satisfied, or are you all happy penalty and YC were the correct result?
16.4 Other ruck offences
(e) A player must not fall on or over the ball as it is coming out of a ruck.
Sanction: Penalty kick
*Adds to an embarrassingly long list of laws he had no idea existed despite playing rugby for a decade whilst at school.*
I genuinely can't recall having ever seen this one pinged before.