I just added this plugin. I created two custom fields. One of them is a checkbox. It's a single checkbox for opt-in purposes. When the value is checked for a user, it breaks the member search page when it runs into that user that has the value checked and stops displaying other profiles after it.
The message below occurs inside the profile box of the user on the Forum Members search page, right below where it says New Member (half star):
"There has been a critical error on this website.
Learn more about troubleshooting WordPress."