Questions that were merged into other questions, before being deleted, ordinarily redirect to the merge target. However, it's possible for users to append
?noredirect=1 on any question that redirects to another for any reason (e.g. anonymous user redirection to targets of unanswered duplicates, migration stubs, etc.) to stop the redirect.
In the case of the latter, it's possible to stop the redirect even after the migration stub was already deleted (and thus see a "this question was removed for reasons of moderation" message). However, in the case where a question was merged (not migrated), and the merge stub was deleted, adding
?noredirect=1 does not stop the automatic redirect. Example (if you have 10k+ on Stack Overflow, access that link while logged out).
This has created a rather confusing scenario in this meta question. I could have sworn that if a merge stub is deleted, accessing it with
?noredirect=1 used to show a "this question was removed for reasons of moderation" message, but that appears to no longer be happening.
(I haven't tested this out as a 10k+ user, but based on the comments of that meta question, I assume that it works properly for them and they see the deleted merge stub.)