# On voting to undelete an answer that's been deleted by a moderator

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.

• Can I ask what post specifically you're talking about here? I (as a mod) have a few ways of deleting things, although I don't know what stops other people from voting to undelete – Mithrandir24601 Mar 11 at 10:09
• This is the question at issue. – Mark S Mar 11 at 14:49
• OK, so, it was flagged (by a non-mod). This flag was marked helpful by a mod - I don't know/can't remember whether or not it was deleted because the flag was accepted (i.e. automatic deletion) or the flag accepted because it was deleted. Reading it now, I'd say it was deleted because it's just not reasonably possible to make sense of what it's saying, so to me, the flagging and deletion were valid. If a bunch of people come on here and say that they think it should be undeleted, I can do that though – Mithrandir24601 Mar 11 at 15:06
• not that I remember it explicitly, but given my comment there it's likely I was the one to flag it. I know I would do it now. The problem with that answer is that it's a series of links&quotes with virtually no real explanation. The answer looks knowledgeable and useful on a cursory look, but imo it's not actually answering the question... or meaningful at all really. Case in point, the first sentence/comment. How is linking a random post about general scattering theory in QM relevant to a question that is essentially about understanding some graph theory notation in the context of QWs? – glS Mar 12 at 18:14
• the rest of the answer is similar. Like, does the sentence The tree is the algorithm and the line is the measurement, mechanical: 0=reflect 1=transmit make much sense to you? I should probably also note that that user had a habit of posting similarly put together answers back then. Sometimes this style of aggregating more or less relevant links and quotes can still be useful, but other times, like the case at hand, it is everything but, imo. – glS Mar 12 at 18:17
• Thanks! and I understand your positions and agree that the answer is haphazard, and the sentence above, taken even in context, is confusing, but from my (very cursory) study of the question the algorithms do have to do with reflection along a line when the tree is evaluated to $0$, or transmission when evaluated to $1$, This line corresponds to the extra nodes $r'$, $r''$ added to the root $r$. If I (or someone else) were to answer the question we would likely refer to such reflection/transmission. – Mark S Mar 12 at 19:20
• The downvotes measure the quality of the answer. It normally takes seven (7) votes to undelete, which is a pretty high hurdle to me and if I were to vote to undelete many more would be needed to undelete. But that seems different than not being able to vote to undelete at all when the answer is deleted by a moderator. Again I won't hang my hat on whatever decisions but how would I answer the question while equitably indicating the original answer, now deleted, had touched on many of the details? – Mark S Mar 12 at 19:24
• I'd say for this particular answer the deletion was also probably correlated to the user's history of making similarly cryptic posts without providing clarifications. I don't doubt there is some meaning to be found in it, but I'd argue there is in a similar fashion as to how a Nostradamus will manage to predict the future. That said, I agree that there might indeed be merit in saying that such questions should just be downvoted if people think so, and eventually potentially deleted via the regular voting process; deletion might have been a bit much in this particular case. – glS Mar 12 at 23:39
• but then again, I don't quite see the problem in potentially having to reference that answer if you want to write your own. There isn't really any original content other than links to other papers and brief quotes from them, and most of the linked papers are the standard ones you'll find upon briefly googling the subject. I'd say if you want to still give credit to pieces of the answer, you can still include the link mentioning it's a deleted answer (assuming it stays so). – glS Mar 12 at 23:42