Question about adding people to a hydra account

[Virtuoso]

Rule #11 of the Forum Rules and Guidelines says the following:

Do not ask or give your password to another user unless the account has specifically been set up to act as a hydra (i.e. a joint account).

Questions have came up in the past whether or not it is allowed to add/remove people from a hydra account (i.e. Democracy). Recently I was added to a hydra account that was set up for modding a game (which has been cleared by the moderators). I feel there needs to be a definitive rule clarification about what is and what is not allowed in terms of adding people to a hydra account. Furthermore what are the rules change if the hydra account was setup as a mod or a playing account?

[BigYoshiFan]

What difference does it make? What shouldn't be allowed?

[kuribo]

I've been told before by mods that you are 100% not allowed to add new members to hydras and must create a new one. This is why DGB/me/FG became Serene2 instead of just replacing Fate in the original Serene