actually it depends on which instance you have chosen and the privacy policy of chosen instance.
my instance doesn't require an email so it's pretty much anonymous like 4chan. but I want to find out some different forum or board that isn't Lemmy.
Edit: plus you can't post without an account on Lemmy.
It would be interesting to make a Lemmy fork that doesn’t require login and registers all posts as anonymous@(instance). Would probably get insta defederated by every other instance though lol