Over Two Meters Tall!· Registered
It sounds like it does come down to the irresistable force vs. the unmoveable object as far as arguments are concerned. Unless we get a story of the Khan being found and fought in the Webway by a Harlequin, who just so happens to use the Kiss, we'll just be speculating till the cows come home.On one hand you have the incredible lethality of the weapon, and on the other the incredible durability of a Primarch.
On a more practical basis, I agree with you that if one of these things did get loose inside a Primarch, then he's toast. All the sterner stuff and not knowing their physiology stuff is just BS. Uber 40K weapons can kill a Primarch, and this certainly ranks in that category. Perhaps if a Harlequin masked the Kiss as a piece of toiletpaper, boy wouldn't that be a surprise!