@frissdiegurke then it is settled. Though... now I am at a crossroads. "I sum fastidium," albeit wrong, makes me unique (a little bit more that we all are). Yet, Fastidum Sum, other than being correct, it sounds better. Correcting it, thanks!
Don't ask how I came across this one, it's a strange one, to reproduce,
This only happens in Firefox as far as I can tell,
Open a topic via ajax from a category, close the tab with ctrl + w or with the X on the tab, press Ctrl Shift & T to reopen that tab. Hold the back button on the browser and click the first link that takes you back to the category where you came from.
You get this:
However the URL is that of thr category.
It actually looks quite nice, but should probably be an option if people ask, and not a bug. (Would tie in nicely with the related posts issue that's on Github)