@samerivertwice Firstly, "MSE is not for tackling open problems is obviously false" is not so obvious as stated. In the past we have definitely rejected them when the open problem is asked as a question, e.g. [this](https://math.meta.stackexchange.com/a/9977/29335). I'd think that would be by definition research level, and even on mathoverflow [they do not seem to accept such posts](https://math.meta.stackexchange.com/a/9879/29335).
On the other hand, I don't know what type of posts you two are actually discussing, and I could see some content about "why doesn't this approach work" being f…