It'll still be there. But any time - ANY time - you have a forum like that and you're AWARE of it, you're giving tacit acceptance to what is said on it, and could be legally be considered responsible for any bullying or criminal behavior that occurs on there.
Directors of large programs should really take the time to create an official Twitter account, SnapChat page, subReddit, Tumblr blog, Discord, Tiktok, YouTube account, and the like - all linked to an official ISD email. That way you can point to the fact that anything said ANYWHERE ELSE is not officially sanctioned by the ISD or by you, since you have your official linked platforms.
Even if you leave them mostly (or completely) inactive, post one or two things a semester if not more often if possible. Either you control the narrative, or the narrative controls you. The other reason to create them? If some kid creates the "Official Banana Slug Band Twitter" (go Cal Santa Cruz!) it's much more of a pain to prove that it should belong to you than it would be if you owned the name beforehand.