This is the thing. It's additional info in the events. Don't know if a normie user would understand that. And what about niche clients for a subset of users tagging the events? Very easy to track them.
I mean... There may be some.... interesting clients, eventually.
If you go from client to client, it's similar to a browsing history.
Sure I could see you swapping from desktop to mobile and so on
Or from some furry dating client to the interracial porn client to the Mormon homemaking client. LOL I mean, okay, obviously switch npubs, but still.
I think any client that injects non-critical tags into events by DEFAULT is wrong. Build a better UX that enables users to understand their purpose. I will continue to build tools that enable hard-core users to strip these tags before signing. Client's can break this if they want, but I hope they choose to accept the signed result as authoritative.