I’m suggesting we prevent more than one trust level group from being added in the settings because it’s redundant. It will cause confusion if people think they can add several and exclude others without knowing the implications. But I’m happy to hear arguments to not do it and I’m not saying I know exactly what we’re going to be doing here.
The main thing I am focused on with the _allowed_groups site settings is figuring out how to simplify the descriptions while remaining as clear as possible about what the settings do. It’s not uncommon for people to get confused such as here:
I haven’t thought so much recently about trust level groups and category security and I’m not aware of problems that people have reported, so thanks for raising that. We could display a warning when a trust level is used, and link to the documentation.