[Goose]

I can't remember where I heard it, but a "rub" is legal provided that the rubbing receiver makes some kind of effort to get open and/or present himself to the QB by facing him with hands up.

I don't think that is correct. Clearly, a receiver can't go down field, push the defender away, then turn around and present himself to the QB/catch a pass. I think the contact has to be "incidental" or initiated by the defender. Both players have a right to their position on the field. Both players have a right to the ball. So if the offensive player can make it plausible that he didn't initiate the contact or was trying to catch the ball, it probably isn't OPI, or at least it is a credible no call. That is why on the one touchdown the I think we both agree was OPI, the receiver made a big show of turning around and putting up his hand after he had blocked two guys and the ball was past him. But it wasn't a credible acting job.
A legal "rub" play occurs when the defender has to run around another offensive player who has a right to be where he is on the field. There are gray areas, probably too many.

On the last TD the Alabama DB was basically tackling the Clemson WR doing the rubbing so I don't think that was OPI.  But at least one other TD pass earlier in the game was.

I agree with your evaluation.

[Goose]

I can't remember where I heard it, but a "rub" is legal provided that the rubbing receiver makes some kind of effort to get open and/or present himself to the QB by facing him with hands up.

I don't think that is correct. Clearly, a receiver can't go down field, push the defender away, then turn around and present himself to the QB/catch a pass. I think the contact has to be "incidental" or initiated by the defender. Both players have a right to their position on the field. Both players have a right to the ball. So if the offensive player can make it plausible that he didn't initiate the contact or was trying to catch the ball, it probably isn't OPI, or at least it is a credible no call. That is why on the one touchdown the I think we both agree was OPI, the receiver made a big show of turning around and putting up his hand after he had blocked two guys and the ball was past him. But it wasn't a credible acting job.
A legal "rub" play occurs when the defender has to run around another offensive player who has a right to be where he is on the field. There are gray areas, probably too many.

On the last TD the Alabama DB was basically tackling the Clemson WR doing the rubbing so I don't think that was OPI.  But at least one other TD pass earlier in the game was.

I agree with your evaluation.