Backstory: Back in 2013 the American Dialect Society appointed because Word of the Year. People had begun using a new syntax: noun-phrases and adjectives could now follow because. In response Geoffrey Pullum on the Language Log corrected all dictionaries everywhere and argued that because is not a conjunction but a preposition. With this new usage because has not changed or added to its part-of-speech. It is simply acting ever more like the preposition that it is.
That's all old news. Recently I saw a similar use of which:
The earth was formless and empty, and darkness was hovering over the surface of the deep, which, ugh. (Source.)
Simply by rules of analogy, would this usage make which a preposition as well?
I've found another sighting:
That was it. I walked out (no one clapped, which, fair), and for the next half hour I sat in the quiet dark, as three more people took their turns. I peeked through the curtain a few times. One person was lying down. Another was just sitting there.