I suspect this is substacks default styling. It actually doesn’t set the tab-size which defaults to 8. However there seems to be some funky font-rendering going on so it adds an extra half (or maybe three-quarters) of a space per tab-character.
You can see this your self if you edit the markup in your browser’s inspector and add `contenteditable` attribute to the surrounding <pre>, then navigate down a line... it will jump forward just by slightly less then a column per indent level.
You can see this your self if you edit the markup in your browser’s inspector and add `contenteditable` attribute to the surrounding <pre>, then navigate down a line... it will jump forward just by slightly less then a column per indent level.