The official app purportedly has a shit ton of interaction tracking. I can’t find the link anymore, but somebody on HN even claimed what they wanted to track was so invasive that he walked out of a job interview for Reddit.
What I can say for sure is that the new Reddit “shreddit” website is absolutely fucking full of tracking. I reverse engineered it for reasons, and every interaction with UI elements was reported back before the actual interaction was allowed to take place.
They definitely gain more value out of user data from interaction tracking than they do from their comments.