I never understood this. I can delete anything from Nexus and reupload something else in its place. Is this supposed immutability just a convention that's followed?
Yes, you can, if you manually interact with it. Most people don't do that because why would you? You generally use it as a proxy for maven central and similar and to upload your own internal artifacts through maven-publish. I'm not sure if it's the standard setting, but Nexus should typically be configured to prevent you from overwriting non-snapshot versions.
