Does anyone have an experience with the North Face S8K boot?

No, but you can find plenty of boots that are more expensive yet rated higher. There's a reason for that. North Face is relatively new to the technical mountaineering boot world so I'm staying away for now.
When it comes to high altitude extreme boots, my safety and toes are with the extra money.

Makes sense.

Notice they were listed on Backcountry for 40% off, but couldn't find even a single review/reported use online.

Yeah I saw that too. Not unusual for that steep a discount for hard to sell sizes, but they had 9-12 at 40% off. That tells me all I need to know. You'll rarely see that for La Sportiva.

I purchased the S6K Verto Extreme which could be considered their smaller brother and found them poorly designed, I had to have the zipper changed since the one that came with could not stop from splitting and I had to pull really hard to zip them since the material has virtually no stretch. These boots are filled with little things that just annoy you. But for 300$ I still find that they were an OK find. At full price I would look into the new La Sportiva G2 SM.

Anyone who has used these notice that the rough exterior of the inner boot tears up the soft inner fabric of outer boot? The soft black felt with perforations is all chewed up after putting on the boots only a few times. I'm not necessarily concerned that the soft inner fabric is damaged, but I want to eliminate any damage to the reflective silver layer underneath the black fabric, if possible.