It looks silly of course, to have columns running in and charging through holes in the enemy line and then hitting them in the rear, or whatever you manage to pull off with them. I'm definitely not accusing anyone of doing this, don't take it the wrong way. I do it myself because it works.
So how to make this tactic not work is the question. Of course you could remove TC... but I don't view that as a solution to the problem, to me that would just be removing half the game to "solve" half the game's problems.
One way I think would be to make maneuver columns move as slow as any other formation when within musket range of enemy troops (not cannons). This way, assuming maneuver columns do behave worse under fire than lines, there won't be a reason to attack in column. Any other ideas?
I don't think simply increasing casualties that maneuver columns take would be enough, because it's possible to run around the enemy line's flank so fast that they won't be able to wheel fast enough to get any shots off, so often you don't even take any casualties when attacking like this.