​@Lupercal reach out to RC support and ask them to remove it via the “Composability” process. The way composability works is that an additional setting appears in the Admin Portal > Users > Roles section. This means you would be able to assign or remove access to the message feature with a custom role. See picture below.

If “Message Tab shown in Main Navigation” is unchecked the user won’t see Message.

or alternatively RC shuts Message down completely for your account.