> A Typographical Mystery

I suspect many people here just haven't used typewriters extensively. You can adjust how the paper is put in before you start typing. You can move it up a little, over a little, etc.

You can type the whole thing without subscripts, then put the paper in a second time, adjust it a bit and get all your subscripts.

All you need is a repeatable spacing template. And that is easy to do with transparent paper. With three different pieces of parchment paper, you can get three different repeatable levels (regular, subscript, superscript) fairly easily - you just run the paper thru 3 times. Align it, then pull the parchment paper out.

You can do the same thing vertically so you get nice repeatable grids.

It's a lot of work, but not a "mystery".