Seams like Automattic went the right way with using WordPress and their P2 Theme for internal use. [0] Departments, groups, or people can have their own "boards". Within that you can write posts or comment, mention people. The P2 theme is great for one liners to walls of text and pictures. Plenty of plugins to expand as need desire...

[0] https://ma.tt/2009/05/how-p2-changed-automattic/