1. My IP might leak somehow, despite Tor being configured correctly (maybe a bug in Bitcoin Core causes this, or maybe my bitcoin.conf file gets ignored somehow and I don't realize it for a while (this was an issue I ran into when I specified a non-default data directory, but it hasn't been a problem using the default)).
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Thanks.
Initially you worried about IP leak due to possible bug on Bitcoin Core. When full node connect to other nodes, it can send and receive transactions from/to other nodes. By passive listener/spy, i refer to one of these,
1. Other full node connected to your node.
2. Other device who use same WiFi/LAN connection.
3. Your ISP.
4. Your VPN provider, assuming you use VPN.
So those party could know your full node (along with your real IP address) broadcast certain transaction. But they cannot be fully sure since the transaction itself doesn't contain any information about which node that initially create or broadcast it.