That is a question I've thought about a lot.
If you are "good" at a language, I think knowing the fundamentals or syntax is not enough, because this only requires a month or so of intensive learning.
It also requires deep understanding of the surroundings, for example,
Knowing to hack something in a language is achieved very quickly, so it is not a good indicator. And then it really depends on the language.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.