1.James enjoyed the movie more than Susan. 正确

   James enjoyed the movie more than Susan did. 正确 （操作词替代）

   James enjoyed the movie more than Susan enjoyed. 错误，enjoyed缺少宾语，as为比较副词，从句必须加it 。

   James enjoyed the movie more than Susan enjoyed it/the movie. 用it正确，用the movie错误。此时不可重复名词，必须用人称代词指代。

2.He speaks English as well as his mother does. 正确（操作词替代）

   He speaks English as well as his mother speaks. 错误（及物动词缺少宾语）as为副词。

   He speaks English as well as his mother speaks it/English. 用it为正确，重复名词为错误。

以上二个句子，以省略谓语动词或采用操作词最为常见，也自然。重复动词较为笨拙，但不算错误。