I have a niche, active forum with some very good user content. Other websites happily link to it (organically) because it's actually useful, I'm doing no SEO, just following Google's official best practices.

- The topic owners sometimes delete their posts or leave my site requesting for all their data to be removed. No problem, happy to do that, normal user lifecycle. 
- I'd hate to have all these inbound links to my old content to 404. I've noticed in Google Search Console a lot of organic, high-quality inbound links to removed content on my site that just 404 and eventually die, it's embarrassing and also quite a waste of good links. 

1. Should I 301-redirect the removed content somewhere? 
2. Redirecting to the front page does not seem ideal (but possible), 
3. maybe redirect the removed pages to a higher-level category page? 


What is the best for usability? Is there a way to keep those quality inbound links, would be very detrimental to lose them.