Compared to other social networks, Reddit is a bit more barebones in terms of features and therefore also in terms of privacy settings. Here’s a handy list of the things you can do to harden your Reddit account.
Content visibility: Here you can select whether or not
posts to this profile can appear in r/all and your profile can be discovered in /users. I’d disable this.
App authorization: Review periodically, disable app accesses as needed. Less access means less potential data compromises.
Search engine indexing: Disable.
Log outbound clicks: Disable.
Two-factor authentication: Enable.
(This used to be called Personalized Ads, but Reddit has since expanded its “personalization” options)