It would be the Markdown, because in recent mobile version it's not possible to use markdown directly. I've to edit my answers each times if I wish to use markdown. Answers/pages look more attractive with proper markdown and it also make easy to attach sources.

Same argument I like to give for Image attachment .

Next, Night Mood, Notification, relevant questions suggestion , act. act..

I like to mention, musing is much more better than many other platforms on steem-blockchain.