So what have this Great Person achieved in real life? Besides learning Ruby and writing some MtG guides?

If you want to be a serious thinker and make your criticisms better, you really need to improve your research skills. That comment is lazy, wrong, and hostile. Curi invented Paths Forward. He invented Yes/No philosophy, which is an improvement on Popper's Critical Preferences. He founded Fallible Ideas. He kept Taking Children Seriously alive. He has written millions of words on philosophy and added a lot of clarity to ideas by Popper, Rand, Deutsch, Godwin, and so on. He used his philosophy skills to become a world-class gamer ...

Given that he is Oh So Very Great, surely he must left his mark on the world already. Where is that mark?

Again, you show your ignorance. Are you aware of the battles great ideas and great people often face?Think of the ignorance and hostility that is directed at Karl Popper and Ayn Rand. Think of the silence that met Hugh Everett. These things are common. To quote curi:

It’s hard to criticize your intellectual betters, but easy to misunderstand and consequently vilify them. More generally, people tend to be hostile to outliers and sympathize with more conventional and conformist stuff – even though most great new ideas, and great men, are outliers.