Yup, I saw this article too. Notice that it is the left inner guide that is being cited as the culprit, the one that I think also went out in mine.

I'm hoping somebody has seen enough of these to know if it is always that particular rail that fails, as this is the only one that was replaced by the mechanic.

If there was just slight piston/valve contact, would the car still run? Or does this failure tend to have a binary outcome (entirely catastrophic, or entirely okay?) Perhaps a related question -what is happening when incorrect valve clearances lead to rough idle?

thanks gregga!