I wonder how Manny can be cited in the first place because surely the referee saw the tangle and at the time did not think anything from it warranted a card - it's only the headbutt that was missed.
We make a lot of assumptions in a vacuum of facts about what was seen and not seen. You can't tell me that any person that saw the head butt would ever say 'well that's a yellow' so how can it be that if the Lino saw it, he is saying yellow?
I still think both will spend time on the sideline with Manny less than O'Donovan. It's a dirty cheap shot and really cannot believe people are trying to defend this or make it to be nothing when it happened after the whistle and there is a photo of the damage done to O'Donocan prior to head butt.
Ordinarily yes, only if missed / not dealt with. In this case it was cited as an "obvious referee error", presumably because O'Donovan should have been given straight red regardless of provocation, and Manny a second yellow (or nothing, depending on one's point of view regarding the elbow, as discussion here shows).