I did manage to get this working. Text is rendered on a full-screen quad overlay like a HUD. The positions of the text in the 3D world are projected into screen space, and those points are used to render the text to the 2D overlay texture. When the world is zoomed out, the text moves but doesn't change size, so it is always legible.

There could be more work done to keep the text from overlapping when zoomed out too much, but that isn't even needed for this data view.

But man, did that take longer than I thought.