Hehe, I was waiting for someone to catch that. Give the man a CEEgar!
I already fixed that a couple of days ago, it's actually not a line, the lines are correct. What you are seeing is shading that I recycled from my Mk IX template and forgot to adjust to match the short span ailerons. My shading skills are pretty weak, Greebo and Kev do a better job of it than I do. The VIII, IX, and XVI are similar enough that I've been able to share layers between templates to speed things along.
Of course, I have to make sure what I'm sharing is correct for all types. For example, I was able to import my IX lines and rivets layers for the VIII and XVI without much of a problem, but there were some changes to make with the wing lines (C vs. E, short span ailerons vs. full span, wing tanks on the VIII), and some differences with the rivets (ie. the access panels for the empty MG bays on the XVI are 'cleaner looking' due to use of spot welding the skin to the stiffeners beneath rather than riveting, and the E has no blisters on the top outboard panels unlike the C), and of course the back end of the VIII is completely different due to the retractable tail wheel, and the use of a circular inspection cover instead of the large rectangular electrical access panel under the left H Stab. Stuff like that.
Mk VIII, universal or 'C' wing:

Short span ailerons, wing tanks, standard wingtip.
Mk XVI, 'E' wing:

Full span ailerons, clipped wingtip (those two silver dots just inboard of the panel line separating the wing from the tip are the wingtip attachment bolts, you could have either standard, clipped or pointed wingtips installed), note the fewer rivets on the MG panels and no blister. Not shown, but another diff is the gun camera port is in the right wing root vs. left for VIII, IX. The large cannon blister on the game's model is incorrect, too far fwd. I think it's just the 'C' wing blister moved outboard, the E wing blister should start about 25% of the way back from the fwd edge of the cannon access panel and end at the rear edge.
Yes, I'm a GEEK...