That seems pretty likely to be true of Github. But for Stack Overflow, I would be really surprised. Stack Overflow has had a huge and thriving C# community from the start, and it's got so much page rank that questions about any language, "web" or not, are likely to lead there. The only languages that seem likely to be underrepresented are ones that are mainly used by people who learned them long ago and aren't gaining any more users (like MUMPS or something), since those people are unlikely to have questions.