I think the fact that all of your posts are tagged with your userid means they can all be traced back to you, making them all personal information. It's not hard to see how, for example, some employer might get ahold of your Reddit userid and crawl through your post history, looking for any opinion of yours that they don't like.

There is almost 14 years of posts and comments linked to my account. While I'm always careful to not reveal any personal information online, if you mine through 14 years of reddit content I posted I guarantee you that there would be enough little nuggets of information there to figure out my actual identity.

You are sharing a lot more than you think you do. Here is a good example of how much can me determined from a single short video: https://www.linkedin.com/posts/gabrielfriedlander_youve-got-...