I was surprised there wasn't a feature request for this already.

I recently drafted a post for a community call that Clare and I are co-hosting. We planned to share it in groups we're both in, plus one that only she belongs to. We can already cross-post, so collaborative posts feel like a natural next step. I wanted to invite Clare as a collaborator so we could edit the draft together in Hylo instead of in Google Docs.

With this feature, several members could edit the same post at once while it's in draft (perhaps including suggested changes)

Once it's published, if anyone edits the post, the other collaborators get a notification.

A user also reached out via Intercom mentioning:

Can there be a "markup" discussion, where more than one person can edit the same entry? I've been at annual meetings with Word on the overhead and motions and resolutions shared live.