[acheron]

> The point isn't to remember D_x is a linear operator--math isn't about memorization. It's about understanding the context where this is a useful fact and knowing how to figure it out.

Totally agree with this part.

> Post it to the internet and you get ridiculed and mocked for it so that you wish you could forget it.

Telling everybody you meet about a basic fact that you just learned is mildly cute when a 6-year-old does it.

It's great that this person learned something that was new to them, sure. But that doesn't mean that they need to shout about it to the tens of thousands of their closest friends who read the front page of HN.