The new indentation logic makes nesting more meaningful by encouraging linear conversations (until a tangent conversations appear). Although the norm when replying to the last item in a conversation thread is to continue the conversation, the new model does not provide a way to start a tangent conversation intentionally to those users that just want to make an off-topic comment to the last item.
One way to support that is to consider as tangents those comments where the author of the previous comment is explicitly replied to (i.e., the reply starts with a mention to that user). That is, If I'm at the initial indentation level (level 0) and I reply to the last comment by Bob starting by "@Bob..." my intent is likely to make a side comment and the system can support it by posting it to a new indentation level (level 1).
We can apply this logic to the first indentation level (where mixing tangents and main conversation can have more impact in terms of noise) or to all levels (where there is a risk of the approach being abused and leading to "diagonal conversations").
Below, I created an example conversation which illustrates how the proposal may help to better structure a conversation in some specific cases:
Example Conversation: "Who invented the telephone?"
- Anne: "It was Bell"
- Bob: "It was Yuri Gagarin"
-- Anne: "@Bob we are talking about first time sending voice through a wire, not people to space."
With the current model, the last comment would be at the initial indentation level, which is not terrible, but may get int he way of someone just scanning the initial indentation level to check the proposed answers to the initial question.