Your confusing a for loop with regular code.
If you made it a for loop it will show everysingle text message.
maybe try
Code:
public e_r_hud(id) { // e_r_hud is a ResetHUD event
new m_id = random_num( 0 , MAXMESSAGES )
set_hudmessage(200,100,0,-1.0,0.35,0,6.0,12.0)
show_hudmessage(id,"%s",Messages[m_id])
}