It says
WHAT now?
Patreon's guidelines say this about incest:
We also do not allow other fringe sexual fetish creations, such as incest, necrophilia, or fetish creations that is hard to distinguish from non-consensual sex.
We understand that some topics on this list such as incest or rape are a little bit more complicated because these situations are, unfortunately, part of real life. As a result, when reviewing these types of creations, the Trust and Safety team will take into consideration context including personal, historical or educational narrative.
For example, survivor stories or fiction such as Game of Thrones or Lolita are allowed on Patreon.
So, they contradict themselves in their own guidelines. These are fictional stories and fictional characters, so they should be fine, but they are made to cater to certain fetishes, so is that the problem? Even though the main character isn't real, and neither are the other characters that the main character is having sex with?
Seems stupid to me, but Patreon does what it does, I guess.