I can imagine if someone is not familiar with the foreign name, it may be difficult to tell where the given name ends and the surname begins. Perhaps then it's better to write foreign names with spaces for clarity. What is the norm in Japan?
For example, when writing the name Mary Smith, is it more common to write:
スミス メアリー
or
スミスメアリー
=should be a double hyphen゠instead. See: Why are equal signs used to substitute an English hyphen? and = sign in a katakana name – Mar 24 '19 at 20:31