punctuation - Comma before "and that" in a compound object

1. You should have known that he is quite adept at what he does and that he has the best conversion rate.


2. You should have known that he is quite adept at what he does, and that he has the best conversion rate.

Which of the above two sentences is right? I believe it is the first one, as it appears to be a case of compound object and hence should take no comma.

Also, if there can be a case without a compound object and the second sentence has an 'and that' to start off with, what should I do?

Is it similar to 'so' and 'so that'?

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