So let me open by mentioning that, though I do personally try to look at every single post in these forums you can imagine that the volume is extremely high and I can miss posts. In the future, if you'd like a response from me, please tag me :)
Now, as stated above by many, currently there is a penalty to a ship's throttle and throttle response if a ship comes in contact with the white line. Most people are unable to hit targets that are riding the white line because a ship that is on the white line doesn't move in the same fashion as a ship driving along in the open ocean. Experience typically is the best way to correct this, you get used to seeing how ships react on the white line and it starts to become second nature.
That being said, the large majority of people that hit the white line, I would say in most cases do not intend to do so to evade the enemy fine. Because TBH a good player can typically wreck a ship that is riding that white line.
If you feel this is incorrect, or a player is abusing this mechanic you can send a customer service report in with a reply attached and our CS reps will review the footage.