he was more amused by it than would have been
Hi. I’ve made a sentence as follows. Does it work?
The joke wasn’t very funny, but he was more amused by it than would have been if he hadn’t got carried away with it.
If it doesn’t and only “than he would have been ...” is correct, then why can we omit the subject between “than” and “were” in the sentence below?
More cats were ginger than were tabby.
Could you please explain when a subject after “than” can be omitted? Is there any guidance?
Thank you.

Question

he was more amused by it than  would have been
Hi. I’ve made a sentence as follows. Does it work?
The joke wasn’t very funny, but he was more amused by it than would have been if he hadn’t got carried away with it.
If it doesn’t and only “than he would have been ...” is correct, then why can we omit the subject between “than” and “were” in the sentence below?
More cats were ginger than were tabby.
Could you please explain when a subject after “than” can be omitted? Is there any guidance?
Thank you.

Answer

Great question.  You can change verbs and omit the subject in the second clause, but if you change tenses, you need to repeat the subject.

GOOD: More people like ice cream than hate it.
BAD: I love my current wife more than loved my ex-girlfriend when I was dating her.
GOOD: I love my current wife more than *I* loved my ex-girlfriend when I was dating her.

This is part of the idea of "parallel structure."  If you use the same grammar on both sides of a conjunction, you can omit repeated structures, but if you use different grammar, you have to say all the parts of each clause.

Answer

Beside, does this sentence work?
If no-one had cheated, the score would have been lower than actually is.