On the Admissions: Candidate Changes homepage, why are some of the "Submitted By" fields blank in the Recent Activity section?

The "Submitted By" field is populated if the user who submitted the form has a Person record prior to accessing it. If a person record does not exist yet for the person submitting it, then the value is instead set as "None". A common example of where you would expect to see a "None" value is if an inquiry form was filled out by a completely new family.