Definitely something worth doing and perhaps a good "next iteration", rather than within the existing.

I think so too. In order to be able to display further data of the author, further data (last comment, last post, last vote etc.) would have to be requested. So far, these are not stored in the redux store.

I've assumed that the URL you've used ends with /bookmarks [...]

Right. In section bookmarks I added an additional div component that contains the sorting options.

What's the URL for your bookmark branch?

Maybe you've missed my reply to your comment so far. I linked the branches there. The main parts are finished. The texts and a few little things still need to be done.