Payjoin is one of those Bitcoin improvements that deserves way more attention than it gets. The core insight is simple but powerful: if the sender and receiver collaborate on a transaction, they can mix inputs in a way that breaks the common input heuristic. This doesn't just improve privacy — it also reduces the footprint on-chain, which benefits both parties' fees.

What I've found interesting over the years is how underutilized it remains despite being practical and spec'd out (BIP78). Most people default to coin selection patterns without thinking about input leakage, which is exactly where Payjoin changes the game. I spend a lot of time analyzing Bitcoin transaction patterns and cycle behavior, and privacy practices like this shape long-term HODLing strategy too — knowing you're not broadcasting your stash through input clustering matters for conviction.

The video and writeup you linked look solid for getting people started with actual implementation.