I’ve noticed that obscene, offensive posts get deleted fairly quickly, perhaps automatically based on the large negative downvote they get. But I have not noticed offenders quickly being given penalty time. Does this happen more slowly via moderators? Is there a mechanism for moderators to be aware of what the member did if the post did not get flagged before being deleted?
Physics SE does not have an automated system for removing offensive posts. Posts with 3 delete votes from high rep users or 6 spam or rude or abusive flags are deleted automatically. As far as the Stack Exchange software is concerned, no new post is ever deleted without human intervention, though old, abandoned posts are sometimes deleted automatically.
That said, there is at least one third-party automated system I am aware of that scans posts, notifies users of potentially bad posts, and occasionally flags some of the more egregious ones on the behalf of users who have opted in.
There are automatic methods to ban users from asking questions or posting answers, but these are both not visible to other users. Users can also be given a warning instead of a suspension. Only full suspensions (i.e. penalty time) can be seen by other users, and those can only be issued manually by a moderator.