Said the other source: "I don't see where foam is going to hit an RCC and break the (RCC). I can see more likely where it might break some of the support structure underneath it, a T-seal potentially, or shear a bolt or something. But inherently, this is a very weak area."
Oxidation, corrosion, fatigue- any one of these factors, or a combination of two or more, might have played a role during the impact event, allowing the RCC's to sustain greater damage.
Then again, the RCC's may have been in tip top shape, yet due to the force of impact of the foam, one or more attachment parts might have been damaged causing the RCC's to partially detach.
Some of the links I saw on the NASA web indicated that 1-2mm pinholes are a distinct possibility, and usually has a void beneath them between the central CC core and the Silicon-Carbon overcoat. I wonder what effect a plasma stream in the rarified low-oxygen upper atmosphere would do in burning the carbon core, and how long at Mach 16-18 it would take to breach into the interior.
Burn damage on recovered debris just inboard of the door indicates a plume of hot gas spewed out of the well's forward inboard corner in the direction of the shuttle's centerline. Recently recovered debris indicates the possibility of a similar jet from the outboard forward corner of the door."
If the glove in front of the RCC was compromised, that would put the plasma streams behind the RCC. I also recall that RCC #1 was found, and it had a burn indicator on it's outboard edge -- did it show the direction of the burn? I don't recall it said either way.
I think there's a lot more at play -- some of which you indicated -- than just the foam block hit at liftoff. I hope they get all of the relevant pieces together to prevent another catastrophe.