My 17" just got sat on. It lived! . I left it on the couch and it was covered by my sweater.
I'm typing on it right now. No dents/scratches, hinge is fine. I guess aluminum isn't too fragile
The aluminum does dent or bend pretty easily. You probably got lucky because it was on a soft sofa that could spread out the forces. You probably don't want to put it on the countertop and sit on it.