What Queentoshi said is correct private group is the best for now because if the group is open without a proper moderation, scammers will use the opportunity to scam people in the group in the name of the brand and it will affect their reputation.
I have seen some groups using bot to moderate it users but we still see scam complains in those groups and that means using bot is not the best as well. But it helps temporal moderation and also it limit the level of spamming the group.
TBH, automated tools only helps up to a certain extent. Also lifts the workload of staffs. The best course, would be to combine it with mods who are present by shift so chat is essentially moderated all the time.
They can always set a bot to moderate posting of links and other things that will lead players to being scam. I think main reason for private group is for exclusivity probably they offer some exclusive bonus in there that is only available to certain users that reach the required VIP level.
Honestly, I preferred the private group over public group since it’s clean and moderated properly. An d at the same time less competition on claiming bonuses.
Hm. I'm not sure about exclusivity as the invite link is still available in public--on their website. Essentially, a lot of people would still be able to join. Public chats are just easier to jump into as they are searchable by its @.
In any case, just saw their reply and looks like they have switched to public. This is still better IMO from a business standpoint as you'd want to grow your general communities as much as possible.