Salah virtually never goes down when fouled.Keys is a buffoon. It is scarcely worth considering the opinions of someone who has never played the game at a high level, nor done a refereeing course....but has managed to get himself fired for saying stupid things about a referee.
Firstly, the FA are not going to overturn a call made on the field where there is no obvious error of judgement - and there was absolutely contact. It was soft, but it is impossible to know how much of it is deliberately going down easy, and how much is a smaller man off-balance getting shoved as he tries to shift his balance. The FA will never overturn a referee's call on that.
Secondly, it was a clear penalty. The only reason it is even vaguely controversial is because of how stupid a foul it was - arms extended into Salah's body, perpendicular to the line of sight of the referee, preventing Salah from completing a move. The referee has a better view of it than any of the camera angles. Salah going to ground is essentially irrelevant to the actual rules violation, though of course we all know that he probably doesn't get it otherwise. A defender who uses his arms to impede an attacker in the box is just inviting the referee to award a penalty.
I think Salah has learnt that when you are running in one direction, and a defender tries to push your upper arm & shoulder in the opposite direction, just roll with it an go down.
I'm not sure it would be enough to bring me down, however I haven't been struggling for half a season with a shoulder injury.
Well done Mo Salah.