Reddit is known for censoring subreddits the admins do not like or when they're involved in some drama, they have a specific algorithm to filter out Trump's subreddit from /r/all[1][2], the default subs are strictly aligned with the admins' political views, and recently the CEO mocked Facebook's knowledge of their users data saying that at Reddit they know not only what one publicly speaks (such as in Facebook), but also their users "darkest secrets" (in an interview about advertising on Reddit).
[1] https://voat.co/v/MeanwhileOnReddit/1373659
[2] https://www.reddit.com/r/shittychangelog/comments/59s3ao/red...