lightdm-1.8.5 with lightdm-gtk-greeter-1.6.1 still shows the user list when I set [LightDM] greeter-hide-users=true in /etc/lightdm/lightdm.conf. The following post also seems relevant: https://forums.gentoo.org/viewtopic-t-989610.html
Does this happen with the latest version as well?
Indeed, the issue was my fault rather than any bug: greeter-hide-users=true should be set under [SeatDefaults] instead of [LightDM] (where the option was documented so misleadingly). This works both with lightdm-1.8.5 and lightdm-1.11.9 (the latest one I have tested). Sorry for the confusion created.