In case you didn’t know, you can’t train an AI on content generated by another AI because it causes distortion that reduces the quality of the output. It is also very difficult to filter out AI text from human text in a database. This phenomenon is known as AI collapse.
So if you were to start using AI to generate comments and posts on Reddit, their database would be less useful for training AI and therefore the company wouldn’t be able to sell it for that purpose.
Upvoted content is not higher quality. An AI trained only on the top posts of Reddit would be very funny though.
They could filter posts by time, but that prevents any further data from being used which still limits the value of Reddit to buyers. Even all of Reddit pre-AI is probably too small to be useful indefinitely.