I'm the original one that complained - and now that I used it as a bookmark reference (instead of being linked from HN) I do see the benefit of the back button. Maybe only have back button navigation if there is no existing history. That way, links to the tool don't hijack existing history items.
With replaceState you can change the URL without adding an entry to the back button list. So you can have a back button that takes you back to HN and a bookmark reference.
