We have changed the default main page to the “Latest” version. If anyone wants to keep the previous version, they can go to their preferences and set the “Categories” version. There are other versions apart from these two.
The “Latest” version provides more information about the last discussion, and it gets closer to the spirit of this request. However…
There is an important detail to consider here. Showing the username and the excerpt to quickly scan through last posts in the comments would mean that every single post would have an entry, but this is not how Discourse works. Discourse bumps topics as they are updated, and users see one line per topic regardless of whether there is one comment since you last visit or 50. This makes the topic lists more usable, otherwise busy discussions would take a lot of space in the list.
Still, in case it is useful:
Discourse doesn’t support this. Maybe with some CSS… but given that most topics show multiple user avatar, I don’t think this would look good.
This isn’t supported for last posts. And again, showing the last post would anyway mean that users would miss older unread posts in that topic. There is a possibility to add the except of the opening topic, to give people an idea of what is the discussion about.