It's normal for HTML forms to be submitted when the enter key is pressed while focus is in a text field (note, note a textarea, nor I think any other types of field). But this can be changed, so we don't necessarily have to make it submit it. We could also set the enterkeyhint attribute, which would help mobile users know what would happen (doesn't help desktop, as far as I can tell).

If we expect the form to behave similarly to the normal wikitext editing form (i.e. what's familiar to users) then "enter = submit" is probably a reasonable way to go.

Can't we just change the form to use an actual form tag ala <form @submit.prevent="handleSubmit">? Then you get said behaviour for free. VisualEditor already knows to intercept the Enter key.

Yep, I think that's the simplest way. And do we need to change the button to be of type submit as well?

And do we need to change the button to be of type submit as well?

Presumably!