Should it be possible to overwrite it? Do we want to make it disabled for real, remove the styling, or something else?

I do see why this would be implemented - I imagine it's to discourage changing it accidentally since maybe changing the created user would remove someone's permissions to edit it. But "fake" disabled styling isn't the best solution here for sure.

Isnt it the case that the input is in fact readonly but the button is not disabled.

IE it is showing that you cannot type a username in the input

I think you're right Brian, but it also gives the impression that the button is (or should be) disabled also, doesn't it? Because those are disabled styles, not readonly (which should be different imho)

On FF a new user is selectable and is stored. Related #39233

correct. but you cannot type a username directly because the input is indeed readonly.

The best option is probably to change it so that there is just a button and text instead of a button and readonly input

Readonly input is appropriate, because it's significant info, will be submitted with the form, and should be able to be read by screenreaders etc, but the visual affordance should be different than that of disabled fields.

This is boils down to a styling issue. Not sure if it's part of Bootstrap or our overrides.

Technically it is correct, just looks a bit confusing - maybe only for me. Closing now and thank you for reading!

I agree with you Christiane, it is a little confusing