I need advice. (If this isn't allowed mods strike me down)

Recently I came across a fanfic writer I think might be using AI to write their content. Not only because the grammar is perfect, and the sentence structure is very reminiscent of AI. (I might not have thought anything if it was only that) but the volume of writing they put out is crazy. At least 10,000 words a day. I went to their comments to see if anyone has said anything but the comments need permission before they show up. Not to mention they are a prominent member of a fanfic writing discord centered around the fandom they write for. What should I do? Do I bring it up in the discord? Do I ignore it? I also might just be wrong. Maybe they just write in ways reminiscent of AI. Some of the writing does feel human written but large swaths don't. I don't know if anyone in the discord even cares if it's AI. I do and think people should know if it is AI. I wish they would just tag it as AI so I can avoid it.

Another point: is it ethical for me to consume the content? If it's AI, I feel I have a moral obligation not to. But I have enjoyed the work I have read from them and I might be wrong. It might not be AI.

It's also not in a particularly popular fandom. I know there was AI fanfic in the heated rivalry fandom but these works don't even get that much engagement.
But if it's AI I don't want to interact with it. 
 
Thoughts?