He's a protagonist in this very by-the-numbers shonen series. He's going to be completely oblivious of it.
I don't think stability is the point. He wants it to have a vicious toothy edge.
I WAS surprised that it was something Inosuke himself did. The chips are so evenly spaced and perfectly shaped, that I assumed he just had the sword made that way. Not chipped them out himself with a rock...he's quite the little sculptor.