Leibniz's proposal and similar ones are about a language intended to represent knowledge (formal concepts), and usable by people (with training).
I'm talking about simply a translation layer. It doesn't "know" or symbolize anything on its own -- it's merely a central mapping between all constructs in different languages. Nobody would read or write in it directly, and it couldn't be used to make inferences or anything like that.
What Abstract Wikipedia is proposing is actually quite similar to what Leibniz proposed, an intricately detailed map of knowledge and true propositions.
What I'm proposing is vastly less ambitious and vastly more useful: just a way to store the meaning of text in an intermediate representation that belongs to no single language. But that representation doesn't bother with what are facts or propositions or anything like that -- just entities and relations that mapped to however we ultimately understand languages in the real world. And assisted with a ton of ML, rather than built up from elementary propositions or set theory or something.