Design a machine learning system that makes stock predictions from Reddit comments.

While directly predicting stock prices solely from Reddit comments is unreliable, a more robust approach involves extracting a 'social media interest' signal from these comments. This signal can then be integrated as a feature into a broader machine learning model that incorporates other relevant financial data for price prediction. Key challenges in this system design include acquiring high-quality, representative training data and establishing rigorous evaluation metrics to assess model performance accurately.