Thank you for the information.
If this Civ has a griefer problem, I would hope their own community members can take care of their own problematic members or keep them in line for the day that’s in it.
If not, then people can just stay away from their event and let them be children in their own little corner of the universe. I’m sure the Discord moderators and network of event streamers will be keeping visitors informed, which has been a standard for NMS community events in the years I’ve taken part and attended.
Every festival seems to come with griefers, whether they’re a part of the festivities or not; my experience with past community events is that there are always helpful people on hand to distract them, track them and of course send out the warnings. Unification Day etc is no different.
You can’t stop them from showing up to any publicly advertised community gathering, it’s exactly what they seek out. All you can do is be prepared for the inevitability.
I would hope this does not put off people from joining and taking part, as they always eventually get bored and go away. If they have their own little event space to get their childishness out of their system, well that may have unseen benefits to the event as a whole.
I know I will be staying away from any PVP events at community organised days, as I always do, not my vibe, so thankfully I was going to be staying away from their event anyway.
The event, from my understanding, is open to all, and to refuse them an event space, I would only imagine, would embolden them to go and wreak havoc on everyone elses.
The idea of this festival, having read the About section etc, seems to be about celebration and inclusiveness, and that’s the mantra I want to carry with me going in, rather than make people fearful that awful things will happen.
Griefers are gonna grief, and community police are going to police. Just as they do with every UD and community event that’s come before it.
If everyone avoided things because of the potential or presence of griefers, Hello Games would pretty much never run an Expedition. Lets not let them spoil the festivities pre-emptively like this.
edit:
Sorry did not see this until after I responded
I know nothing about them or their past or what they may have done to your community, but I am all about change and rehabilitation and giving people that chance. Communitie members, leaderships and mantras also change over time within online spaces, so lets hope this is the first sign of turning a new leaf.
If it’s not, well then all we can do is hope that some day they do, and learn how to LARP as an actual pirate legion within the community instead of a bunch of childish immature griefers.
We hope you have an incredible weekend! 
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