Can see is about establishing lines of sight. Eg you cannot teleport to the darkness around a corner. It can be assumed that shadow monk was not meant to be used exclusively with characters with darkvision. That means it is not an expectation that persons be able to see into any darkness. It means you may teleport into the darkness you can see without seeing what is inside it... Ergo teleporting into the spell darkness is no different.

"Space you can see" is about establishing lines of sight. For example, you cannot teleport to the darkness around a corner.

It can be assumed that the Way of Shadow monk was not meant to be used exclusively with characters with darkvision. That means it is not an expectation that the character be able to see into any darkness. It simply means you may teleport into the darkness you can see without seeing what is inside it... Ergo, teleporting into the spell darkness is no different.