Yep. Every transaction you make potentially leaks a little information about other transactions to/from your bitcoin wallet.
That's why I always say "bitcoin anonymity is complicated" and "bitcoin transactions are more private than credit card or bank transactions, but less private than cash transactions" or "staying completely anonymous while using bitcoins is hard."
And that's why you won't find (or, at least, shouldn't find) any claims that bitcoin is anonymous on the bitcoin.org home page or in the bitcoin source code.
What can you do? Use separate wallets. Make your donation address an instawallet or mybitcoin address that you don't use for anything else.
Let's imagine that I want to hide myself belonging to a bitcoin address (because BTC on it are illicit). I could find only two ways to sell bitcoins and not give myself away.
First, sell BTC face to face, in this way they will not be able to bind me to a bitcoin address with criminal coins. But on the other hand, the person with whom I will exchange will have information about me. If something happens, he will be able to give this information to the police.
Second, if you cannot whitewash illegal bitcoins, they must remain illegal. In this case, you need to use the escrow service without KYC and AML, and sell your BTC for Monero, for example, then sell Monero for fiat.
Of course, I always use vpn/tor.
Question is, can I really sell illegal BTC in second case and anyone anytime cant find me.
I will be grateful for the answers.