A marketplace integrated in steemit.com is important I think so people can earn and buy straight away without logging into another site, people could have an extra tab on their profil called "store" or something with all their offers and the site would also have a "marketplace" tab with all products for sale. If you think about it the most difficult thing to build in a market is the escrow part and this was released already right? The rest is pretty easy to integrate.

The second important feature is a way for the site to automatically suggest to people friends or groups that they could potentially be interested in.
This is why facebook and twitter are so successfull because as soon as you register you get familiar people pop up, this is key because it directly create a safe feeling to the users. As opposed to steemit where people register and they feel very lonely and insecure.

Also regarding the point you made, imo differentes languages don't need to be on a different site, its just a few words per language to translate and a filter per language option.

I would also want to see how many people are currently online on the site.

One last feature is to allow history to be viewed entirely, as it is now I can only see my last 20 comments.

Anyway, good job on the list. I think it covers pretty much everything that needs to be done.

I wish steemit inc would set up some bounties for some of these features. It's good that it is open source but you need incentives for devs to build them.