This question looks in imminent danger of being closed on the grounds that it's a pure mathematics question. This is something that happened a lot when I was more active on the site, and is one of the reasons I'm less so now. I'm wondering (a) whether the on-topicness of maths-as-used-in-physics is something that was ever formally discussed, and (b) whether the current community really finds it desirable to ban such questions.
I realise there's a strong tradition of defining this site's topic as being "only questions about physics." The question is whether "physics" here should mean "what physicists do" or the much stricter (and more epistemologically suspect) "what is in the physical world." The linked question above is a good example, because it's clearly technically about a mathematical concept (Dirac delta functions), yet the topic is also clearly something that was developed by physicists, is taught on every physics syllabus, and is of interest to every physicist.
I also realise that there is a mathematics stack exchange where this would be on topic - but in many contexts it is often said that the existence of other Stack Exchange sites should not affect what's considered on topic, so I think that is not relevant here.
To reiterate, my questions are
Was a consensus ever explicitly reached on the on-topicness of such "purely mathematical" questions, and where can I find the discussion?
Is it desirable, to the current community, to allow questions about the mathematical concepts on which physics is built?
Edit: Ah, the difficultly of searching meta. I've found a previous discussion on this topic. The accepted answer, with +16 votes, says:
a question which focuses entirely on mathematical details, whilst perhaps appropriate for the mathematics SE, should be kept on the physics SE if it is motivated by physics, even though it may not necessarily be regarding how it is precisely applied to a physics problem.
which would suggest that the linked question is just on topic, period. Still, it seems worth bringing up again to see if that's still the consensus, and perhaps to remind active close-voters that the agreed policy isn't quite as exclusive as they might think.