So all this is supposed to be another way to interface the purely functional stuff with the rest of the world without the use of monads?

No. As far as I can tell, the author that originated thread containing the post I linked was attempting to achieve something akin to taint-checking vai a mechanism he dubbed "Intent typing", which doesn't seem to appear on the internet outside of his reference.

However, as I attempted to describe, the concept of "Unsafe" in Haskell goes much deeper. A salient reference: This is the "back door" into the IO monad, allowing IO computation to be performed at any time.

Unfortunately, it leaves out the explanation of why it is necessary to incorporate this "backdoor" into the language.