If you reuse a conversation for multiple characters, you can give them character-specific variety by applying a "dialect". For example, in place of "Hello" a sailor might say "Ahoy". One way to do this is to give each character a text table of dialect variations (e.g., "Hello"-->"Ahoy", "friend"-->"matey", etc.). Then you can add an OnConversationLine method to the Dialogue Manager that replaces the plain phrase with the character-specific dialect version. For example, "{Hello}, {friend}!" might become "Ahoy, matey!" for the sailor.
This package contains a script and example scene to do just that:
DS_DialectExample_2020-02-28.unitypackage
Side note: This is the same thing that Quest Machine does to apply dialects to its quest giver characters.