After rummaging some more through the forums, I realize that the Dialog feature is too rigid and there are too many things that are hardcoded in it. I'm sorry for wasting your time with it, but I've decided to go with my own custom dialogue choice system. It will require more work in the long run, but it already looks much better.
As for what I was trying to do - I basically want to have a visual novel-type text system. All of the text in the game has to appear at the bottom of the screen inside a rectangle. The script here is useful for all the text and it looks great when I tweak it a bit, but I also wanted to use the Visionaire's Dialog system. However, when I use that, the text still appears above the characters' heads, instead of the rectangle, like all other text.
Right now, I'm going for a different approach - I'm manually inputting all of the text and the choices. I'm doing the choices through an interface. The problem I'm having now is making the action part wait for input from the player before continuing. I currently have it just looping through the same part of script until a choice is made:
However, clicking the buttons does nothing.
This is, very basically, what I want it to ultimately look like: