If you use reddit's account deletion feature, your posts, comments, and other metadata are not removed from reddit's servers or public view. Only your username is publicly disassociated with them i.e. changed to read "[deleted]". reddit still retains all your info and the right to share and sell it.

The only way to make reddit get rid of your info is to overwrite (and then optionally delete) all your posts and comments, one by one. Overwriting alone gets rid of the info, because reddit currently does not version posts and comments. The January 1, 2016 Privacy Policy update will give them the right to do so.

Below, I am listing all the reddit user data scrubbing tools that I know of, separated into groups:

Backup

If you want to back your comments up before you overwrite and/or delete them, the following tools may help.

Note that reddit limits comment access via user profile and API to both the 1000 most recent comments and the past 6 months . None of the below tools can access comments beyond those limits. There is no known workaround. A workaround has been figured out, see this post.

Autopager - For Firefox. Implements infinite scrolling for many sites, including reddit. After installing and configuring the extension, scroll down in your comments page as far as it will go to get all your comments on one page, then save as HTML.

Reddit Infinite Scrolling - For Chrome. Implements infinite scrolling for reddit. After installing and configuring the extension, scroll down in your comments page as far as it will go to get all your comments on one page, then save as HTML.

Shreddit - Python-based. Can back up or delete comments, make sure you choose the right option at the right time.

Unnamed Python Script - Python-based. Also requires PRAW. Produces a JSON file.

Overwriting/Editing

Tools in this group overwrite or edit your posts and comments with an exit message.

You may optionally use reddit's account deletion feature after running any one of these tools, so that your username is publicly disassociated with the overwritten posts and comments, as well.

Note that reddit limits comment access via user profile and API to both the 1000 most recent comments and the past 6 months . None of the below tools can access comments beyond those limits. There is no known workaround. A workaround has been figured out, see this post.

Reddit Overwrite - GreaseMonkey-based. Compatible with most mainstream browsers when a GreaseMonkey-compatible scripting extension is installed first. More details are available in this Voat post. Overwrites all your posts and comments with a short, civil exit message telling people that you are done with reddit. Not auto-censored by any subs.

Reddit Overwrite Extended - GreaseMonkey-based. Compatible with most mainstream browsers when a GreaseMonkey-compatible scripting extension is installed first. More details are available in this Voat post. Overwrites all your posts and comments with an extended, opinionated exit message that expresses dissatisfaction with reddit management and announces that you are moving to Voat. Auto-censored by several default and large subs.

Reddit Overwrite Extended With List of Alternatives - GreaseMonkey-based. Compatible with most mainstream browsers when a GreaseMonkey-compatible scripting extension is installed first. More details are available in this Voat post. Overwrites all your posts and comments with an extended, opinionated exit message that expresses dissatisfaction with reddit management and announces that you are moving to a reddit alternative. Not auto-censored by any subs. RECOMMENDED.

Reddit Overwrite Extended Edit Only - GreaseMonkey-based. Compatible with most mainstream browsers when a GreaseMonkey-compatible scripting extension is installed first. More details are available in this Voat post. Prefixes all your posts and comments with an extended, opinionated exit message that expresses dissatisfaction with reddit management and announces that you are moving to Voat. Auto-censored by several default and large subs.

Complete Deletion

All listed tools overwrite your posts and comments with null, inconsequential, or random data before deleting them.

You may optionally use reddit's account deletion feature after running any one of these tools, so that your username is publicly disassociated with the deleted posts and comments, as well.

Note that reddit limits comment access via user profile and API to both the 1000 most recent comments and the past 6 months . None of the below tools can access comments beyond those limits. There is no known workaround. A workaround has been figured out, see this post.

Edit: If you know of other tools that can help, mention them in the comments and I will edit them into this post.

Edit 2: If you've already deleted your reddit account, but less than 90 days ago, you may still be able to use one of these tools. Contact reddit admins, ask them to reinstate the deleted account (tell them someone in your residence deleted it without your permission), and once your account has been reinstated, follow regular instructions. If it's been more than 90 days, they probably won't do it, but you can still try.

Edit 3: This is already stated in the linked "more details" post, but it bears repeating here, because people don't fucking read. There may be issues with recent versions of TamperMonkey, the version of GreaseMonkey for Google Chrome. The ideal platform for running GreaseMonkey scripts is GreaseMonkey on Mozilla Firefox with all extensions disabled, except possibly an infinite scrolling extension. Try that if possible.

Edit 4: The claim of a 6 month limit on one's access to one's own comments was based on apparently inaccurate reports. Testing has revealed that it is not in effect on one's access to one's own comments, but on contributing to threads only. This development has also been edited into the body of the post.

Edit 5: A workaround.for the 1000 comment limit has been figured out, see this post. This development has also been edited into the body of the post.