If you just assume that everything you put online is being saved and used by everyone and everything you'd be better off.

This used to be the default when I was a kid. Never give out your real name. Never give out personal information. Don't post pictures or videos of yourself or anyone you know or that contain identifying info like addresses, landmarks or anything else that might make it easier for someone to figure out where/who you are.

All the data you send to Lemmy can be viewed by just about anyone. Including your votes. Deleting something doesn't necessarily get rid of every instance of your content across the whole fediverse or anything that's scraping data (including other users who just have a habit of saving every single thing). If you have an app that lets you share content and you find a "deleted by creator" post, you can even copy the post body and paste it elsewhere to see what it said prior to the deletion.

Always assume everything you put anywhere on the internet is going to be saved somewhere whether you want it to or not.