It would have to be Bitcoin Talk, but I refuse to wade into that cesspool again. The last time I was there it was all spammers, scammers, and shills. The majority of posts were about gaining higher post counts without spamming so users could post more meaningless garbage so they could increase their stake in signature campaigns and earn some bits.

So, yes, the correct answer to your question is that it’s Bitcoin Talk. A better question, however, would be which Bitcoin forums are quality places to converse.