One thing to be aware of is that there is currently, AFAIK, no now (since 0.19.3) a way to "disable" a JWT.

Before that, once you had created it, if you leaked it, your account was, as far as I can tell, definitely compromised.

Now, it is possible to logout, to mark the JWT as "invalid".

I will add, as a disclaimer, that I have not checked if that as Nutomic highlighted below, there are conditions (password change, etc) under which any or all JWT (user, instance, etc) become invalid. So do audit the code if this is something that concerns you. As far as I am concerned, I treat the JWTs as extra-sensitive information, and store them only on machines I own.

Edit: correct information in the light of Nutomic's comments.