This argument makes no sense though - Vardy (and the rest of them) put his leg there knowing that the defender will invariably collide with it - as you say later on "he has tried to "buy" a penalty". It is a deliberate act designed to make the ref think he has been fouled.
Which I'd hazard a guess at 50% of all penalties being the case.
The striker is perfectly entitled to put himself in a situation to get a penalty. If the defender collides with him, the ref has the decision to make whether it is one or not - but it isn't simulation.
I think people are just confused and think simulation is anything that is trying to get a penalty - it's not. Simulation is solely where the striker makes an action to try and get a penalty where minimal contact, if any, is made.
There's more than enough contact and reasonable doubt for this one on Vardy to be waved away, and given the referee should be 100% sure before calling it a dive, then he's had a complete howler.