|August 18th, 2015|
|meta, facebook [html]|
What happens when you can reply one-level deep is that each top-level comment provides a topic and a jumping off point for a discussion with back-and-forth. In yesterday's comments we had simultaneous discussions on loosely coupled topics without them interfering with each other, and each of those discussions felt coherent.
In a massive discussion you would still have a problem with needing to break things down further, to get sections of the discussion small enough to talk in, but with the size of interactions I've had on Facebook one level of replies seems like a good fit.