Hello,
This comes from experience with actually running lots of events. Especially for events that are free, have limited spaces, it is not desirable to "assure participation" to registrants. I'd like to see Matukio should do the following:
a. When someone is registered, the email they get should not tell them they are "Participation Assured" - Staying within the current framework, it is more effective to put status "Awaiting Confirmation"
b. When the admin logs into the backend, he can evaluate the registrants by any means and then change the status to "Confirmed" or "Participation Assured". These should then get an email update stating that their participation is now assured