Investigating why Steam started picking a random font

Out of the blue my Steam started picking a random font I had in my user fonts dir: Virgil, the Excalidraw font.

That triggered me all sorts of emotions, ranging from laugh to total incredulity. I initially thought the root cause was a random derping from Valve but the Internet seemed quiet about it, so the unreasonable idea that it might have been my fault surfaced.

Who doesn't love a good technology mystery story?