Correction, the following is not the case: > because when I set [org-indent-indentation-per-level] to e.g. 5, I > would expect the amount of indentation when I run org-indent-mode to > increase appropriately, but it doesn't, it's the same as with the > default value of 2.
I got confused when testing the different variations, I was expecting the indentation change to happen in the wrong place. Sorry for that! So to be clear: setting org-indent-indentation-per-level to 0 is broken and leads to the aforementioned error. Setting it to a value >0 behaves correctly, as in, the indentation of the heading levels changes accordingly. Cheers, David