Let's assume that I have two accounts on my Metamask wallet
Could, actually, a hacker find a method that allows him to understand that those two wallets belong to the same Metamask wallet?
When metamask is unlocked, it knows the balance of these 2 accounts. Metamask is not a full node, it must have contacted a server,
sent the 2 addresses to this server and asked what their current balance is.
Not a hacker, but now the world knows that those two wallets belong to the same Metamask wallet.