I believe what the OP is talking about is "Content Siloing", which is something reddit does through subreddits. Each piece of content belongs to a specific silo within the site, and that silo is highly curated to only allow relevant materials.

Currently the tag system we have in place is doing a terrible job of siloing. Tags are being used inappropriately - causing most of the tag pages here on steemit.com to be just a jumbled mess. Occasionally a large stakeholder in steemith will issue a threat saying "I'll flag anything with inappropriate tags", but that's not a good solution, as it requires constant vigilance and is impossible for a single person to do, especially given the limited payout windows.

To draw the comparison further between reddit and steemit, steemit.com's homepage right now is just like /r/all on reddit. It's shows everything, all tags, sorted by the "hotness" factor (payout in our case). It honestly doesn't make for a homepage that's all that appealing, except to those with a lot of power. There's also probably good reason as to why /r/all isn't reddit's homepage, and instead reddit uses a silo'd approach to the default subreddits.

To answer your question of "what features do they need to have", in order for steemit to move to a silo'd approach, we would need:

• A mechanism to allow for one "tag" that would act as the Silo. The post would only show up under that tag.
• Limiting each tag page on steemit to only show posts that used that single "Silo" tag.
• A mechanism to allow the community to adjust the silo'd tag on a post. For example, a great post that used "gaming" as the silo tag and "league of legends" as an additional tag, but is 99% about league of legends, should have the tags swapped so "league of legends" is the silo'd tag. Pseudo-moderation.

I don't know that any of this would necessarily work in the steem ecosystem, but I think it's worthy of the discussion. Currently what we have isn't good, and a better solution needs to be worked out. Hopefully the OP, your comments, mine and everyone else's will help lead to that conclusion.