@Le_Doctor_Bones
Oh, I know it burns, I'm just remembering the days when I would throw the paper into a fire, have it land underneath the fire, and then get real disappointed it didn't even catch for like fifteen seconds (mind you I was like 6 at the time and not very smart).
Also, we know that the fireplace had a fire due to the materials, but not when the paper was thrown into said fire. Keep in mind that this guy is...not the most competent villain (given how his introduction and his defeat filled all of like, five pages). Also apparently magic is involved when it comes to the making of this paper somehow, so... I dunno how magic burns, man. Maybe they made the paper from demon trees and it gets like a +1 defense against fireplaces.
Let's be honest here. Matty isn't smart by any stretch of the imagination: he's just experienced. Experienced to a point where you kind of have to suspend your disbelief and keep going, because this world runs on so many rules of cool and rules of convenience that it's honestly not worth trying to justify every little damn thing, because since everything is explained in a hand-wavy way, you can always find a reasonable enough explanation of things.
For example: Matty's building-movement magic moves "buildings", and the basement of a building would therefore be a part of a "building" and would move along with the rest of the structure, much like how the submerged hull of a ship isn't somehow different just because it was submerged.
The position I maintain is that this is basically one-punch-man but with comparatively far less thought placed into world building. It's still fun, don't get me wrong, but the rather soft magic system it uses means that trying to logic it is pointless. Alternatively, you can always go a little beyond the impossible, since Matty's apparent end goal involves fighting literal Space Monsters in his far future.
Like...the fact that Matty's conveniently hypercompetent is the framing device that lets the author show off the neat shit he/she/they want to do with magic. I'm pretty ok with that.