TLDR: While Fediverse won’t directly serve you ads, anonymous bad actors other than Meta can save, redistribute, and even dox you for any information you post here. Anything you post here can/will remain forever on some malicious instance that doesn’t honor deletion requests. So be careful!
Well things that you post on a public social media site… Are public.
If you don’t want your info to be public, don’t post it. Also be aware that people can also archive posts before you delete them. Common sense stuff