BTW, I did notice that the problem was gone during the time that systemd-oomd wasn't
running, so that's definitely the cause. Unfortunately, the mask command alone
isn't enough to prevent it from running, I'd have to either remove
systemd-oomd-defaults or edit some config files. And this really should be fixed, it's
just wrong that anything running in a DE is protected from being killed, while a non-DE
login, or any command run from within that, isn't.