Like the original comment, my original thought was that it was probably something to do with people referring to line numbers on HEAD. A less link-bait title that confirmed this would have allowed me to easily skip this this article which, for my purposes, was useless.
I actually feel that the post isn't even just about people who don't know that linking to a line number in a changing file will result in incorrect information later. I think it's more that when people link to code, they think it doesn't matter, so it's not something they actively care about. So they don't take the extra time to link to the actual commit since it's not a thing they care about.
I feel the authors real value in their article is a call for people to care about correcting their links for programmers in the future. The article would be better served to say, "Why you should care about linking in time to your GIT repo"
