The problem is that when we accepted people admitting to hacking, players went, "OMG, this server allows hacking! People are openly admitting it in chat, and the mods do nothing!" And not only were the mods getting fed up with sarcasm being reported as Hacker reports, but the players and their misunderstanding of sarcasm was starting to make us look like hackers were flaunting their hacks in public without repercussions.
That's the problem with sarcasm over the internet: a lot of people just don't get it.
As such, we adopted a policy that leans on the side of caution when it comes to a joke about something so serious. We'd like to allow for a more lenient policy, but it's easier to just tell people not to joke about something so serious.