[dsr_]

The best way is threading, which combines chronological, unread status, and the tree structure of replies.

Everything else is either an attempt to do less work or an attempt to shape user experiences for your own goals.

Threading requires two data elements per message, generated at the time of message creation: a unique-enough message ID, and the parent message ID. The client needs to have a method of storing 1 bit of state per message, either locally or on a home server. If messages have a timestamp, then a high-water mark is a useful heuristic. If the messages have required subjects, tags or topic groups, you can significantly improve both performance and user experience.

Usenet shall be resurrected, time and time again.