Well it definitely highlights to draw your attention to it as a very simple market tool. Even if you don't like it you have to admit, it does catch your eye. That's what Cipsoft wants because its one of the ways they make revenue, which leads to the first part. I can almost guarantee there is no legal way to turn it off because it leads to one of Cipsoft's revenue streams, so why would they allow it to be turned off.
Maybe if you suggested to them a feature (bought with Tibia Coins) where you could pay to turn it off. Otherwise there is no reason for them to allow it.
Just look at it as a little chore you do when logging on, like collecting your reward but less rewarding