In some ways I think this is a tricky problem since you want users to get deeper into some topics, but not ones that are considered "problematic", but defining those is inherently political.<p>It seems like you could define some idea of "depth" into a topic (based on how far out of normal viewer's patterns it is), and only generate recommendations for items that aren't far outside of the norm, but this would lead to a lack of depth for recommendations in niches.<p>Maybe a middle ground would be to treat sensitive topics differently in terms of "vertical" recommendations, by e.g., explicitly marking some categories as safe and enabling recommendations to go deeper, but only allowing "horizontal" recommendations for unknown topics, and maybe preventing recommendations "into" that topic from the outside.<p>So... if you're watching train videos you might get to see even more niche ones, but welding won't recommend for you fox news, and watching fox news won't show you Alex Jones recommendations.<p>I pick on the right here since it's in the topic (and I'm left leaning myself), but I think radicalization is an issue on the left as well (though frankly my political opinions make me think it is less impactful there, mostly because of the way people radicalize on the left I believe tends to impact less marginalized people or be in terms of policy rather than affecting people that are already beaten down).