Currently, there is no actual way to modify chat log. You either see all together (system, alliance, area, party...) or one of them separately (not system though). I think it would be really nice to be able to create one's own Chat log tab with what one would like to see. For example, I would like to see system notifications separately, and one chat log with party, alliance and whispers only. Also, being able to change the colors for each type of log would be really cool (Traditional guild green color would look nice on alliance). Oh and by the way, being able to actually see in chat log when a player joins the alliance one belongs to, would also be quite nice.