Their post does show up, they posted in #Destiny2 not #Help. IP bans are pretty much pointless and very few companies use them now because they're easy to bypass and ISPs use tech such as CGNAT. Because cross-save is enabled, any bans applied to the account would be applied to the active profile. They need to speak to Xbox to to see if they'll ban the account but it likely will be a no. They are essentially stuck with the account linked, and as the person that linked it has the login, they are now essentially stuck sharing an account until one of them gives up and just stops using it. Bungie won't unlink the account, and there are no exceptions are being issued for this.