Help Please! Showing possession with names

[Hannah Faoileán]

Pick an easier name?

 

[David Newrick]

The way I have always understood it is that if you were talking about something personal possessive to Julius you add the s, i.e. Julius's nose. Whereas something non-personal drops the possessive s, i.e. Julius' letter. Do you see the subtle difference there? However, it is a 'vague area' and most readers would not care or even notice the difference as long as the sentence scanned right.