'Related content' pane

[Bossett]

Is your feature request related to a problem? Please describe.

Discoverability of people, feeds, labellers, etc. is a problem - and there is friction in following/etc.

Describe the solution you'd like

A new pane where the feeds are listed on desktop, or in a 'slide left' on mobile, showing 'related content'. This should gather the top ~5 posters/items by mention into one place with appropriate subscribe/follow/etc. buttons. On a feed page, this will be the current contributors (based on the 'page' you are on), in a thread this will be the participants, if you're mentioning a feed/labeller, it'll appear, etc. - importantly it should list not just people (i.e. how Twitter does it) but also other entities to pull people toward features of the site.