Not sure if this happens alot in other casual alliances but lately ours is frequently having new members join, only to leave the same minute before we can even welcome them. We don’t allow vulgar chat and our preferred language is clearly labeled. If I had to venture a guess, we are getting snooped on to see what ☆ level of titans we are hitting?
Be thankful they aren’t spamming you with recruiting messages then leaving.
They may just check out what the membership looks like, check on what titans, and if it’s not challenging enough, move on.