[CharlesW]

https://litherum.blogspot.com/2019/03/addition-font.html

"So this is pretty cool, but it turns out that the contextual substitution lookup type is really powerful. This is because the table that it references can be itself, which means it can be recursive."

[…]

"So thats a pretty powerful virtual machine. I think the above is sufficient to prove Turing complete-ness."

[raphlinus]

Behdad had this result earlier: https://twitter.com/behdadesfahbod/status/958065026262183936