Hi,
I think Kooyeen said something like you need to change your tense after verbs like 'thought' since they pertain more to your feelings.
And I bellieve Mr. M said that the native speakers intuitively back-shift for the sentences like this:
I didn't know you have a sense of duty.
But for these??
When I met a friend I haven't seen for a long time:
Hi, John. Nice to see you. I didn't know you are married. I am glad you told me you have recently got married. Or Hi, John. Nice to see you. I didn't know you were married. I am glad you told me you have recently got married.
Going into the store to buy candies:
Look, John, I thought this candy is on sale. I was here yesterday evening and saw it on sale. Let's go buy the candy somewhere else.
Or
Look, John, I thought this candy was on sale. I was here yesterday evening and saw it on sale. Let's go buy the candy somewhere else.
I feel for those two examples, since they are not concern with someone's feelings, but pertain to factual scenarioes like being married and a candy being on sale yesterday and today, the need to back-shift isn't there for both of those situations like here:
I thought this car is the best one out there.
I thought buying a house is the best form of investment.
I thought John is the best-looking dude in the world.
I thougt Mr. Lee (who is dead) is someone we could consider as a role-model.