There is absolutely nothing wrong with posting twice a day. Actually, you can post as much as you want. It just makes your account active and engaging to your followers. It is your account and you can post as many times as you like.
What happens after 10k followers on Instagram?
Once you have 10k followers, Instagram will make it easier for you to get people to your website via Stories with the swipe up to link feature. Swipe up is the only way to get a direct link from your Instagram to your other web properties. And, it’s available in STORIES, if you have 10k followers.