Somethings I can immediately think of, but definitely not enough to address the issue.
1. Anonymous student ratings, if the solutions are obviously unclear or unhelpful to the student. A history feature would need to be there so the student can go back and mark a question as unhelpful or wrong even if he realises this after a week.
2. You'd need to separate unclear or unhelpful answers from plain wrong maybe? I don't know what's the line you'd need the draw but if an answer is deemed to be false, the student would be eligible for some in-app credit that he can redeem towards his next question/subscription.
3. Random cross verification of answers? Other teachers would get to judge a random answer from another teacher and provide feedback. Students would be notified automatically if an answer is revised in this way, while also providing the correct solution. Teachers can have an infraction counter or something for the same.
Even if they do absolutely nothing with the number, I'm not putting it in. It's not a question of their intention but my convenience and peace of mind.
Nice topic to build a project but there's one immediate issue I see with the implementation- The books. It attempts at trying to "facilitate" or "drive away" your current mood by recommending books. Most people can't read books because they have an attention problem. Also imagine someone who does read them, and decide to pick up a book reminiscing about the youth just because he felt nostalgic at a particular moment in their life. What's next? How's he to find the drive to actually finish what he starts? If someone's emotionally pretty turbulent, what happens if he keeps starting new books and can't finish any, leading to feel a certain dread when coming back to the reading table because of all the unfinished quotas he has. This kind of feature will go well with someone more like Blinkist or Deepstash in my opinion with overall summary and immediate conclusion available. Then if the user likes the content at a glance, that would be the fuel they need to actually complete a book after they pick it up. Still, a cool project. I do read a lot and I'd probably pick some book recommendations as well.