Does it just make them unable to send you messages? Or does it do anything else?
The official story from the devs is it will put them down the matchmaking queue for you.
Its a bit vague as to how that will actually work.
Its not as simple as just making you not see that player. When you fly around you can be connected to up to 31 (can't say I've noticed more than 16) other players. Some or all of them might be off your scanner range, so you wont actually see all the players. You can't just make one of the 32 players in a system invisible, while still seeing the others.
If blocking works, and there are 10 players where you arrive, you will connect to these 10, and they will connect to you. If one of these players is blocked you wont connect to any of them. You will just see empty space.
If you are in a system with 10 other players, and someone who you have blocked arrives they will not join to any of the 10 players. They will just see empty space.
Things get more complicated if someone in your friends list is connected to your banned guy. Should the game connect you because you want to see your friend, or should it make you not see either of them?
The other part of it is "putting them down the matchmaking queue". This might mean nothing happens unless there are over 31 players where you arrive. Outside of popular systems and CGs thats probably never, so the block might do nothing.
I might block one of the code guys at Diso to see what happens, anyone know if you can unblock someone after you have blocked them?