Yes, this was an April Fool's gag! Relax!
There is no way JokerxHarley could be replaced about any other pairing in my heart – LEAST of all HarleyxBatman. I wrote the ship I found pretty much most repugnant for this.
Look forward to more JokerxHarley writing from me in the future – I still have stories to finish!
Hope you enjoyed the gag! XD