I do this sometimes when I am flying alone or with another like-minded pilot, though maybe not the point of hanging on a stall or going below/too close to VMCA. I don't do it to show off, I just do it to have fun, whether there are people around to see it or not.
I am not sure exactly how much more likely an engine is to fail whenever you are in a steep climb rather than a shallow one, but either way we take risks every day and many of them just self amusement, some will go base jumping some will drive a bit faster than they should, it's all about what is an acceptable risk to yourself.
I wouldn't personally do it with passengers though.