Can't comment on an empty merge request
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6384 added empty merge requests. Thanks, @artem-sidorenko!
I can't add notes to those MRs, though. For instance, I can assign the MR, and add labels - but only through the sidebar, not through slash commands
I also can't see the system notes for my adding those, or communicate with the MR author.
See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7503 for an example.