What on earth are you talking about?
If you don't care care about your ranking, nobody is forcing you to care. (Yet, you might switch to a rival platform because...?)
Yes, in this case it's just a stupid ranking, but in the past there have been more serious fakes, where GitHub has had to step in and tell people a site isn't related to them.
Really now? https://github.com. Done.
If you're so concerned, then if it's not on github.com or not advertised via blog.github.com ... ignore it!
I mean, we're not talking about Phishing here. We're talking about a user who is annoyed that he stumbled upon a site and is unsure if he should like it or not. Almost sounds like an odd form of brand loyalty. "I can't decide if i should like this or not"
How would moving to BitBucket keep you from reading about it on HN?
If after you read about it on HN, you spent lots of time playing with it or reading and arguing in these comments, and you regret spending that time... how can you blame GitHub for that, and again how will moving to BitBucket help exactly?
Yep, it's pretty obvious, really. That you're very confused.