Recently, my question regarding a good introductory book on mathematical risk theory was <a href="https://mathoverflow.net/questions/290071/what-is-a-good-introductory-book-on-mathematical-risk-theory">closed</a> because it was deemed off-topic and not research-level mathematics. 

However, I think that multiple similar questions were not closed and garnered loads of responses. Those include: 

 1. "Good books in Modular Representation Theory" (<a href="https://mathoverflow.net/questions/55983/good-books-in-modular-representation-theory?rq=1">link</a>)
 2. "Good books on theory of distributions" (<a href="https://mathoverflow.net/questions/20314/good-books-on-theory-of-distributions?rq=1">link</a>)
 3. "A good book of functional analysis" (<a href="https://mathoverflow.net/questions/72419/a-good-book-of-functional-analysis?rq=1">link</a>)

It seems to me these questions are similar to mine. I don't understand that my question was closed while these other questions I just mentioned look rather similar to me. 

Furthermore, I think my question *is* about research-level mathematics. The theory of risk measures is a pretty advanced and a difficult topic. So it's not like I'm asking for a good introductory book on, say, calculus.