I kind of feel it makes no sense.

Sometimes Superman can hear things on earth when he's in the outer space or when he's at the fortress of solitude from really FAR away. But then how come he can't hear his arch nemesis planning a plot against him when it really matters?

Correct me if i'm wrong.

Plot.

Plot and he is a fictional character to it doesn't need to make sense because it is not real.

Clark tunes everything out so that he can concentrate on the things. As Superman, he wants to hear as much as possible.

Comic book science together with plot necessities.

But then again being able to hear any sound from any point on the planet is quite a feat. That implies that his super-hearing has some psychic element to it. And that could explain how he hears in space.

In pre-flashpoint they even gave a kind of explanation, Superman explained to Supergirl how to talk and hear in space, that by changing the frequency of how their vocals cords vibrated they could in a way speak at different frequencies, that can travel in the vacuum of space. Frequencies that a kryptonian can hear.

But to be in outer space and hear sounds coming from Earth, perception alone cannot be explained in any way.

@heavenlydarkdragon: what you said

it would be pretty boring and kind of scary to have superman appear and cream someone for merely talking about taking him out.

Superman basically have the ability to take selective hearing (or selective auditory attention) up to Eleven. To the extreme.