I've crafted a small field study to compare how a moderately complex conversation is laid out following three different styles of indentation. The experiment is based on the topic "It's more difficult than it used to be to figure out who is responding to whom" at this page.
- Flow style. This is the original conversation. Comments are posted in sequence, except for replies to previous posts, which are indented in the middle in the thread - interrupting the main sequence.
- Classic style. Same conversation, copied to Mediawiki and following Talk page conventions. You should ignore remarks about where comments are placed, as those were originally made for the Flow-style layout.
- Dynamic style. Based on HHHippo's proposal. A classic threaded model, with the twist that comments in a sequence don't increase the indentation level. Instead, when a single post gets several replies, those are separated by horizontal bars at the adequate indentation level (by limitations of the software - you should imagine it using this visual style instead). This model resembles the classic style more closely than Flow.
I would love to hear your comments about how the different layouts compare to each other.