Repro: 

1. Create a file /etc/security/limits.d/coredump.conf containing following (w/o
quotes): "* - core unlimited" 
2. Log in as regular user
3. Run ulimit -c

Expected: unlimited

Instead: 0

This, in particular, prevents me form having core dump of gnome-shell segfault:

>��$  coredumpctl -1 list /usr/bin/gnome-shell 
>��TIME                            PID   UID   GID SIG COREFILE EXE
> Sun 2017-03-26 17:53:38 +03    3068  1000   100  11 none     /usr/bin/gnome-shell

>�������� 26 17:53:38 t-rex.homenet kernel: gnome-shell[3068]: segfault at 7f57d62fffe8 ip 00007f58227a6965 sp 00007ffee1ee7d80 error 4 in libgjs.so.0.0.0[7f582277a000+be000]
> ������ 26 17:53:38 t-rex.homenet systemd[1]: Started Process Core Dump (PID 1436/UID 0).
>�������� 26 17:53:38 t-rex.homenet systemd-coredump[1437]: Resource limits disable core dumping for process 3068 (gnome-shell).
> ������ 26 17:53:38 t-rex.homenet systemd-coredump[1437]: Process 3068 (gnome-shell) of user 1000 dumped core.

And to prove current gnome-shell has coredumps disabled:

>��$   pgrep -u develop7 -f /usr/bin/gnome-shell
>��3121
>��$  cat /proc/3121/limits | grep core
>��Max core file size        0                    unlimited            bytes 

It looks like this restriction comes in place somewhere inside gdm-x-session
binary, because it has unlimited core size, but his child,
gnome-session-binary, has core size 0