Reviewing the list of highly-upvoted questions without any publicly observable answers, there is one question with what appears to be a good-faith answer that was facially informative although maybe not complete, but nonetheless had more downvotes than upvotes and was deleted by a mod; hence the answer is not visible to the public.
There may be some hidden information or more history about why the answer was deleted and I don't want to second-guess the mod who deleted it; I also don't want to stir a pot if there is one to stir. But I tried to vote to undelete as it takes seven (7) undelete votes to get a consensus, but got a message saying:
A moderator has deleted this post and it cannot be undeleted.
In such a case, is there anything to be done? Once an answer is deleted by a mod, are only mods able to undelete?
The question is, at least to me, pretty good and could engender a bit of research to the curious, but those without the reputation to see the deleted answer might repeat work unnecessarily.