The watch notification button is a link instead of an actual button

Links are used for navigation, buttons are used for actions.

Arguments for it being a button.

This element looks like a button but currently acts like a link (opens with enter instead of space...).
Interacting with this element opens a modal.
This link has an empty href value.

Arguments for it being a link.

This link directs the user to the "Update notification preferences" user journey.
The extra features that a lin provides are useful. E.g. `open in a new tab` is useful when the user is in a (non-realtime) edition session since this avoids reloading the page where the notification change request was made.
It's already a link. Action links are a thing. I looked it up again online and it's not really much of a thing. We have other action links in XWiki but it's probably minor accessibility issues ^^'

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IMO the first list arguments outweight the second ones. This element should be a button instead of a link. If you don't agree feel free to start a forum topic and ping me on it