Actually I loved the beginning of the welcome message (thank you for taking the time on your busy life ...) but passed a few sentences I scrolled down to find the link.

On the feed page, I think you could reduce the text on the sidebar. I dont care about the welcome message, if I'm registered why do you explain me the website again I should already had understand what Sparkmuse is about. I would delete that paragraph and replace it only by the "Create Spark" button (make it big and colorful, I didnt saw it the first time I saw this page)

You can also reduce the "We want feedback" block maybe you can install uservoice or something.

On the spark page the solution appear 2 times at the top of the page and on the sidebar. Why ? Maybe you should put the question and the solution at the top of the page like Quora/Stack Overflow or other discussions board.

Again it's only my PoV. You made a great job .

A lot of your copy focuses on how this is just the beginning, how important this site is to you, and how you want feedback, etc. That's great for someone who already cares, but most visitors to any site are going to be ambivalent until they know what they're getting out of it.

Put yourself in the shoes of someone who doesn't care about you at all. Explain the unique benefits that that person can access right now. Appeal to their selfishness. Focus specifically on things that Sparkmuse enables (right now) that cannot also be said about alternative sites, such as Hacker News. Trim everything else away.