You can't hide that someone sent you 5BTC from someone who can find your BitCoin address in one of your posts. But they can't tell what you did with it. If they see that 5BTC transfer to another account that's never been in the chain before, they can't tell if that's you spending them, moving them to another account, or what. (And for all they know, that could be you sending yourself 5 BTC.)
Sophisticated forensic analysis of the chain might reveal more. That's to some extent an open question.