Look at those two cases:
http://en.wikipedia.beta.wmflabs.org/wiki/Topic:Sl18xph3p9den4ob (deleted topic)
mw.flow.data.blocks.topic has no 'roots'.
http://en.wikipedia.beta.wmflabs.org/wiki/Topic:Sl18xaj7bextx9g8 (non deleted topic)
mw.flow.data.blocks.topic has 'roots'
Since we do allow for both of these to show as their own pages (in single-topic view) and the only difference visually (and semantically) is the fact that one is deleted and one is not, we should be able to also work both of those into our OOUI/DM efforts. That is a little difficult if both replies are different in structure -- especially since having 'roots' in the reply should have nothing to do with whether the topic is deleted or not.
Can we make those two consistent for the sake of our API clients (including consistency in our Data Model) ?