If a sales person changed an email address of a person in Salesforce, will it create a new lead in Marketo or the info will sync back to Marketo and the person remains the same?
Another person is not created if the email address is updated, rather the sync will log an activity of the change data value and the person will just have a new email address. However, if this new email address now matches another person with the same email address, both people will then populate your "Possible Duplicates" system smart list in Database.
What do your tests show?
Retrieving data ...