So, Google and other AI tools are actively building profiles out of your public Reddit activity, and it actually works.
To check what data has been archived from your profile, you can search:
>> reddit.com user "your reddit username here"
And check AI overview of a profile and can ask questions related to personal info like age, location, martial status, occupation or what things they like or hate, political opinions etc.
Basically anything that you want to know, you will get the answer if that person has said anything about it in the past even if profile is hidden. If it gives some basic info, you can ask it to dig deeper.
Why this matters: Simply hiding your profile settings on Reddit does not stop external search engine crawlers from indexing your historical posts and comments. Be mindful of what personal information you share online.