"Don't show me anything said by someone who joined after I did". "Show only <person, writing on topic> pairs with historical ratings above this threshold from raters in the weighted set generated by crawling thusly from this seed set." "Prioritize anything on topic X which multiple people from this set like." At 8am: "Don't show me anything this classifier thinks is a pun"; 8pm: "Show me puns, please". "Show me anything the author thinks is good, if their self-evaluation rating on the topic meets the following criteria." "Don't show me anything dang rates as not meeting criteria X".
Even USENET 30 years ago had people sharing kill files (don't show me comments whose headers match [patterns]). They weren't sufficient to check eternal September, but we can do better now. It seems like there's a rich design space available here that we've not been exploring. What am I missing?