@simon_brooke @marcan my observation here is that “making your whole machine unusable” is true iff the machine is essentially single-user and all of the applications/programs running on it are connected to the X server. Which is probably more likely true for the average Linux user than on more traditional Unices which more often had separation between compute server and display server.

Am now trying to remember the last time I had a unix account with uid > 1000 …