I don’t see a use case for having communities on the sidebar all the time. It should be hidable sidebar if possible.

I would like to suggest that the interface change to a two-column interface where the first column shows all posts and the second column shows the comments. In other words, tapping on the post opens it up in the column next to it.

(Hideable) Communities | Posts | Comments

I also recommend the bottom toolbar is moved to the sidebar as well; with the username/profile on top and settings on the bottom.