[ginnungagap]

I specified I'm working in standard first order logic. And I'm not sure what do you mean with the informal take.

Also intuitionist logic is not my area, but isn't it divided in inference rules for provability and (Heyting or Kripke) semantic for model theory and truth just like FOL?

[mietek]

You may be working in classical logic, but that doesn’t mean the parent poster is. You asserted the parent poster seems to be confused, but what the parent poster said makes sense in a constructive setting. Please see my other comment:

https://news.ycombinator.com/item?id=18756974