Comment # 21 on bug 1229721 from Stefan Seyfried

/var/log/journal does exist:
mixi:~ # ls -l /var/log/journal/
total 0
drwxr-sr-x 1 root systemd-journal 15868 Jul 29 16:14
5acde102e5594ff3bc6496cb06b393f0
mixi:~ # du -sh /var/log/journal/
577M    /var/log/journal/
mixi:~ # df -hT /var/log/journal/
Filesystem              Type   Size  Used Avail Use% Mounted on
/dev/mapper/system-root btrfs  100G   20G   78G  20% /var
mixi:~ # ls -lrt /var/log/journal/5acde102e5594ff3bc6496cb06b393f0/|tail -3
-rw-r-----+ 1 root systemd-journal  8388608 Jul 29 16:14
user-10329@a3038c45f00446faa549a932c744c403-000000000005fb58-00061e36a70a8c10.journal
-rw-r-----  1 root systemd-journal 33554432 Aug 20 20:54 system.journal
-rw-r-----+ 1 root systemd-journal 16777216 Aug 20 20:54 user-10329.journal

mixi:~ # lsof /run/systemd/journal/io.systemd.journal
lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/10329/gvfs
      Output information may be incomplete.
lsof: WARNING: can't stat() fuse.portal file system /run/user/10329/doc
      Output information may be incomplete.
COMMAND   PID USER FD   TYPE             DEVICE SIZE/OFF NODE NAME
systemd-j 206 root 9u  unix 0xffff888b4195f400      0t0 1240
/run/systemd/journal/io.systemd.journal type=STREAM (LISTEN)

journalctl --flush results in a journal message:
Sep 01 20:47:00 mixi systemd-journald[206]: Received client request to flush
runtime journal.

but no changes to anything in /var/log/journal

I also tried restarting systemd-journald.service, but also no change. But a
journalctl --flush afterwards then moved on to the persistent storage:

Sep 01 20:50:24 mixi systemd-journald[206]: Journal stopped
Sep 01 20:50:24 mixi systemd-journald[206]: Received SIGTERM from PID 1 (n/a).
Sep 01 20:50:24 mixi systemd[1]: Stopping Journal Service...
Sep 01 20:50:24 mixi systemd[1]: systemd-journald.service: Deactivated
successfully.
Sep 01 20:50:24 mixi systemd[1]: Stopped Journal Service.
Sep 01 20:50:24 mixi systemd[1]:
run-credentials-systemd\x2djournald.service.mount: Deactivated successfully.
Sep 01 20:50:24 mixi systemd[1]: Starting Journal Service...
Sep 01 20:50:24 mixi systemd-journald[4175]: 36 unknown file descriptors
passed, closing.
Sep 01 20:50:24 mixi systemd-journald[4175]: Collecting audit messages is
disabled.
Sep 01 20:50:24 mixi systemd-journald[4175]: Journal started
Sep 01 20:50:24 mixi systemd-journald[4175]: Runtime Journal
(/run/log/journal/5acde102e5594ff3bc6496cb06b393f0) is 8M, max 314.9M, 306.9M
free.
Sep 01 20:50:24 mixi systemd[1]: Started Journal Service.
Sep 01 20:51:21 mixi systemd-journald[4175]: Time spent on flushing to
/var/log/journal/5acde102e5594ff3bc6496cb06b393f0 is 144.629ms for 2131
entries.

Before restart, the /proc/<pid-of-jounrald>/exe link was pointing to
/lib/systemd/systemd-journald (deleted), now it is pointing to
/usr/lib/systemd/systemd-journald.

My guess is still, the "handover" from initramfs to installed system (with a
restart of journald?) is not working as intended and so for me the journald
from initramfs is still running? But I have no real knowledge how this is
supposed to work anyway, so I might be totally wrong here.