I can’t answer your question about the votes, but posts and comments are retained when you hit the delete button. The only way to delete them is to edit the content beforehand. I believe moderators are capable of restoring posts, but I haven’t checked the comments yet.

There’s no reason where this has to be the behavior by default; federation alone is a challenge but not an excuse. Ironically, when it comes to privacy, a company like Reddit (with sketchy privacy policies) might be better than Lemmy (a series of entities in a variety of jurisdictions where your data is protected by the weakest of all of their privacy policies)