I'm pretty impressed with Movim so far. Aside from having a clean interface and a nice mobile app, it has groups, chatrooms, and editable posts!
One-on-one chat works great too (it's built on top of XMPP so one would hope).
If your pod has XMPP enabled, you can log in to a movim pod using your D* account, and if not, there are plenty of places to get a free XMPP account, including chat.gibberfish.org.https://movim.eu/#try
If you decide to check it out, say hi.
Movim is a kickass distributed social platform, with web client and mobile apps, that protects your privacy, comes with a set of awesome features and uses the industry-standard XMPP protocolmovim.eu