I've been browsing Tildes a bit today and, overall, am enthusiastic about what I've seen. However, while reading a thread, a thought popped into my head that was evocative of an issues Reddit and other tree-based systems suffer from — thread freshness and activity over time both decay quickly.

While reading the thread, I thought "I would comment, but there already seem to be a lot of comments here. If I reply to a specific tree, then that limits people who might see it and respond. Even a top-level comment probably won't be likely to get much of a response."

On Reddit, this leads to repost after repost of the same content in brand new threads, as the activity level of a thread decays and the thread is lost. It looks like one way you intend to combat this is with different sorting methods (Newest, Activity) over various time periods (all time, last 3 days, etc.). Do users feel that this will be effective enough itself, or do they have other ideas to combat this issue?

The way I generally see it, linear threads often beat out tree threads when it comes to keeping threads alive without users having to read through a lot of crap to figure out what the current topic of discussion is, and where it's taking place. (Linear threading models to think of are phpBB, vBulletin, IP.Board, and their ilk. Tree threading models are sites like Reddit, Slashdot, or Shacknews. There are also hybrids, like Metafilter. Please share other examples and their pros/cons.)

In a tree system, I've often experienced the following sequence:

1. Read all top-level replies
2. Read most sub-level replies
3. Find where in the tree the most recent discussion is occurring
4. Realize it's not coherently taking place in one tree
5. Decide not to reply

While in a linear threading system:

1. Read past 2–3 pages of replies to get caught up
2. Add a reply

Alternatively, the linear threading sequence can also be:

1. Read entire thread to see how it's evolved over time
2. Add a reply

An added benefit that is usually concomitant to a linear threading system is that threads are easy to "reactivate" (AKA gravedig) — simply add a new reply and the thread gets bumped up the stack for all users. This is not an exclusive benefit of a linear system. It could likely be made to work with a tree system too. The Activity sorting method may be related, though it's unclear how this functions.