Rename and use multiple "Animation Nodes Object Containers"? When you use a "Separate Text Object" node, the resulting characters/objects are grouped together using a parent empty object, always named "Animation Nodes Object Container".

Is there a way to change that object's name without "breaking" the animation node?

That would be very useful for organizing the objects in a scene.

Which leads to another linked question: is it possible to use more than one "Container" ?
No sorry, this is currently not supported. Maybe it will be in the future but I'm not sure. 

You can however disable the parenting at all in the advanced settings in the node and parent them manually to an object. (Note: you'll have to do this again when you click the update button)