15% seems much too low. I would think more like 25-30% are either fully or partially AI-generated. And we've had ML-backed propaganda bots on reddit long before LLMs showed up.
More analysis would be interesting. For example, are posts or replies more likely to be AI? Did AI cluster in any particular subreddits or promote unusual viewpoints?
This might be one place where AI slop comments actually improves the Eternal September that Reddit is in. Emphasis on might.
I welcome the AI to reddit, better than listening to the echo chamber, circle jerk discussions that go on there.