I have multiple users on my PC - using a variety of keyboard layouts. But modifications to layouts for one user affect the layouts of other users.
So for example if user 1 adds a second layout, it appears on the other users' layouts too.
I've searched a lot, found plenty of people also running into bizarre problems (you have to add a keyboard layout before you can remove it...), but nothing like this. Is my use case just too exotic? Is there something in the way this data is stored that is user independent? Or is it because my user has admin rights that it's being written somewhere else?