Thanks for your query. I have tested the scenario and have managed to reproduce the same problem at my end. I have logged this issue in our issue tracking system and you will be notified via this forum thread once this issue is resolved.
Please use the following code snippet for a workaround.
var doc = new Document(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "test.docx"));
Console.WriteLine("Test first paragraph in last section font");
Console.WriteLine("Expected Font: Comic Sans MS");
// Console.WriteLine("Actual Font: " + doc.LastSection.Body.Paragraphs.ParagraphFormat.Style.Font.Name);
Console.WriteLine("Actual Font: " + doc.LastSection.Body.Paragraphs.Runs.Font.Name);