"Host" and "SYSTEM", why both?

[AAIK]

The game uses "Host" and "System" for messages, shouldn't it be just one of them providing information?

[Skuzzy]

"Host" is specific to the server.

"System" is specific to any given system in the game (flight, sound, input....).

I believe that is correct.  Not in a position to dig into the details.

[hitech]

The game uses "Host" and "System" for messages, shouldn't it be just one of them providing information?

Yes.