They don’t tell you this but actually the main problem with selfcest is that you have two characters with identical names and you need to find a natural way to differentiate the two in your fanfiction. Which is Annoying.
There are two Jons. What do I call them both. Would either of them agree to use another name. Would it be really really annoying to constantly call future!Jon the Archivist at all times. What happened if another character (Elias) Didn’t Want To Call Them That. I can’t just call them future and past Jon all the time that would be clunky. I need to write this fic but there are! Logistical issues!!!!
When Jon gets fingerfucked until he can barely walk by his future self who hates him, is he supposed to moan his own name? How am I supposed to easily and smoothly differentiate between two different Jons for multiple sex scenes? For the Jon/Jon/Elias threesome??