User registration; validate email but don't activate automatically
I think the approach Johannes posted as an answer to the question you linked to is a good one.


Let the user activate the account via email. It makes sure the address exists and he has access to it, because he can't guess the activation URL without the mail.
This activation only makes him become a member of a Users Group without any permissions at all (e.g. 'unverifiedUsers'). To restrict front end access do something like this:

{% if currentUser.isInGroup('unverifiedUsers') %}
    &lt;p&gt;You don't have access rights. Please wait until an admin verifies you account. Thank you!&lt;/p&gt;
{% else %}
    {% include 'partial' %}
{% endif %}

Then let an admin do the manual verification: add the user to a group with the permissions you want.