I tried to streamline the site's header without departing too much from the current look and feel.
The main difference is the elimination of the main menu. Links like "Settings" or "Log Out" are not often accessed, so it doesn't make sense to show them permanently in such a visible location.
I also tweaked the look of the header a little to make it more appealing, giving the background a subtle texture.
The tab shape protruding from the page also reinforces the search box's association with the rest of the page.
Finally, I got rid of the prominent "Add Question" and "Write Post" links, since "Add Question" is redundant with the search field, and "Write Post" is more of a power user feature.
The main activity feed is the heart of the site. It aggregates all the updates to questions, topics, and people you're following.
I didn't stray much from the current layout, but I tried to make the feed less cluttered, and give it more breathing room.
When you need to show a lot of repeating information like this, it's important to give each element a distinct look (by tweaking font weights, colors, backgrounds, etc.) to avoid having everything blend together. This also reinforces the rhythm of the layout.
The current Quora sidebar is confusing. It includes both ways to browse content (such as groups) and unrelated actions (such as accessing your saved drafts or inviting someone to Quora) with very little separation or organization. And on top of that, those are not features that most people use regularly.
I thought it was a shame to waste prime real estate, so I decided to create a new "Recommended" section that includes a mix of topics, questions, and people that Quora thinks you should follow.
This feature already exists for people, so it seemed natural to extend it to topics and questions. This could help solve one of Quora's problem, which is the lack of a good content discovery mechanism.
With the current design, you need to actively seek out new topics to follow, which means you will often miss out on interesting threads.
This is probably the part of the design that's most different from the original. Quora notifications are obvious on the homepage, but hard to access from other pages since you need to hover precisely over the notification indicator to display them.
There is also the problem of the notification indicator being associated with the "home" menu item, which implies that notifications are only visible on the homepage.
My solution was to display them in a pop-over that you access by clicking on your own name. The pop-over also includes less frequently accessed links such as profile, settings, and log out.
While hiding away links can be bad for usability, I feel this solution works well because in this case there is only a single place to look for them.