On February 28th, Chef Operations set the firstname field of the Hosted Chef user records for 55 users to "unknown" from "".
This condition could occur in users created before manage.chef.io disallowed user signups without a firstname/fullname. This hasn't been the case for quite a long time, which is why there were only 55 users with this problem.
Any user previously having a problem with https://getchef.zendesk.com/hc/en-us taking their login information and then blanking the text fields after refreshing the page with no login will no longer have that problem. The issue here is that logging into Zendesk as an end-user requires two items from the Hosted Chef user record to be 0 length:
* email address