THis statement from your documentation is the issue:
"Private ideas portal users
Users can only register for a private portal if they use an email address that belongs to one of the domains included in the Employee portal setting."
THere should be a concept of a private portal (our software is highly competitive and many ideas could be leveeraged against us, making keeping this private vital.) where we have employees (Product team, support, customer success) that need access and the ability to comment privately on ideas before they are shared with the entire portal audience. THe Portal audience would be customers who self register, and we would like that registration to be restricted by customer domain. Right now, if we use the domain restriction, those users are EMPLOYEES and we can use VIsible to employees to hide ideas that arent ready for voting or "public" consumption.
Our only recourse is to turn off registration and import the users directly which seems counter productive and heavy handed given the self serve nature of this portal.
If we could just have a field above USERS which are valid domains (same as the EMployees domain field) that self registering users domains are checked against, this would resolve our issue.
We would like the ability to add a customer organization with Domain(s), and this be enough to allow customer users to register for a private portal. Having to import them is problematic. A flag at the organization level 'Allow users self registration' or alike would be great.
I would almost fully support the OP idea, but augment that allowing an Aha user to approve self-registered customer users, instead of having to enter all approved domains, would make the feature usable to organizations with thousands of customers. We have simply too many customers to enter all the approved domains, or create users for them, or keep them up to date with spreadsheet imports. So, choosing between two bad options, we're choosing to keep the portal public, which means indexed by search engines, available to competitors...
We have worked around this issue using Google App Script. Our clients register by filling in a Google Form, and our app script then creates the account and sends the user an email to set their password.
It would be great to have this feature OR one that allows us to disable the registration link and add custom text to redirect the user to our Help Center or our Google Form.