Do people not understand social media is the 2023 version of a community public square?
I see posting a comment or voting like shouting your comments and votes in a public square. I see no reason to expect privacy in this settings.
Your shouting in a public square and then upset that people heard you and potentially recorded you?
Sure I would agree deleting something on Lemmy has a higher risk of not actually being deleted everywhere. But again it is a public forum. Nothing is stopping anyone from keeping a record of what you said. How many people have deleted a controversial/drama filled post only to have screenshots of it posted later by third-partys?
As long as you can delete the original it is basically like any other public forum. The original is deleted any other copies are kind of out of your control. Yeah it sucks but such is life anything digital can be copied so be careful what you create.