Good call! This just keeps getting better, sharing the URL is such a natural thing to do but of course they need to add the tracking parameters to everything.
In this case it's both tracking and a legitimate feature: being able to place unsubscribe links in the "web version".
I'd argue that this feature is not worth the privacy invasion, but for it to work, you do need a secret in the URL that is always personal.
They could easily have left the unsubscribe in the email, and linked to a UID of the mass mailout text instead for the web view.
The ClearUrls Firefox extension often prevents this...: https://gitlab.com/KevinRoebert/ClearUrls
In this case, the cleaned URL that should have been posted is https://mailchi.mp/ubnt/account-notification