Back in the day, if I saw some braindead karma farming post on Reddit, I took a look at their post history and quite a few times it was a brand new account. I would simply reply “Welcome to Reddit! How has your first [week/day/hour] been?”. I think precisely twice it turned out to be a new human user, the rest of the time they would just delete the comment (or possibly even the account).
In particular, it’s just lazy to escalate to a permaban right away. Even if they have a rule against reposts, removing a post along with a warning not to do it again is sufficient to educate the vast majority of people there who may not have seen the rule and only did it for the first time.
But that would take a few extra minutes, I suppose, to check someone’s post history and see if they are a serial rule breaker. Much easier to just wield the ban-hammer then ignore.