When rebasing the commit end up existing “multiple times”. If such a commit refer to an issue, MR, etc. the issue will get “duplicated” “mentioned in commit XXX” entries in the issue activity list.
As long as all the commit are reachable, it arguably make sense to display both entries, but AFAICS entries referring to dangling commits is not removed. Maybe there are some work running with low frequency cleaning up, but my specific example now is over 4 hours old at least.
Maybe the commit is prevented from being garbage collected because it has a pipeline association? In that case I would “backwards” references such as “mentioned in …” should still be removed as long the commit is dangling from a git perspective.
Example - both these commit is the “same” commit (logically). The second is a modification of the first. All branches referring to the first does not exist.
EDIT: this is GitLab cloud, not self hosted…
EDIT: 3 days ago now, and still visible.