The other examples you mentioned, like Facebook/Twitter posts, are different because they're usually standalone and don't have to be read together with other posts. (You'll notice that new comments on Facebook posts appear at the bottom, because those are meant to be read together and in order.) The one example you mentioned that doesn't really fit here is email threads, which are displayed with new messages at the bottom in interfaces like Gmail.

New at top + box at top => more, usually less relevant (often worse) comments. Because people are more likely to leave a comment and less likely to read others' first.

New at top + box at bottom => fewer, varying quality. Because people are less likely to comment at all. Where there are few comments, they tend to be pretty good; where there are a lot, nobody reads them all, and you get the same as above. And a bit of annoyance at having to scroll past things to get to the box (is this necessarily bad, though?)

New at bottom + box at bottom => fewer, threadier comments, varying quality. People think more like forums. You're also setting yourself up for "fp!", as those stay at the top forever. Similarly, good comments only rarely get a chance to be read by anyone.

New at bottom + box at top => worst of all worlds. Lots of comments, nobody reads, and people get frustrated because theirs never gets seen, leaving the world to the loud and annoyed and nobody else.

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All that said: new at bottom + box at bottom anywhere you intend to have communication. Twitter is both-top because it's not a bi-directional communication platform; it's a shoutbox. The newest stuff matters, and yours is the newest. Focus decreases as you scroll down, and as things get older.

Most chat systems are both-bottom, because you can read conversations like a book, and add yours logically close to where it will appear, and where the likely-most-relevant things are (newest in a thread = likely most relevant to your comment). Focus likely increases as you go down, as things get more relevant; a downside to long-running threads if you have to reload the page, but no real problem if it updates in place.

Choice here can have a pretty profound impact on how people approach and use your system. What do you want it to be used as?

Indeed, YouTube comments work this way, even though they've tried to dilute the sewage a bit by highlighting a few highly-rated comments at top.

I'm still a fan of newest-on-top, but this is a cautionary observation. Perhaps there's some way to have the 'box in middle' – or displaying alongside as soon as you've read enough of the log to avoid the most boneheaded, repetitive comments.

Hm. Anyone be interested in an extension for an in-line reply box for HN? I could probably add it to Flattehn, though it'll take a while.

Are you having a conversation? Then new on bottom.

On a recent blog-like system I did, new entries went on top, but new comments (on the entries) went on bottom. Email works the same way - new threads will sort on top, but within a thread new messages are on the bottom.

Facebook, iChat, Adium, Skype, Colloquy, Campfire, all do bottom.

fixed size comment area, with a scrollbar that starts at the bottom, when you scroll up you load earlier comments dynamically?

That way you can always see the most recent comments in the discussion, and easily scroll backwards through the history to follow a conversation.. scrolling and loading dynamically is a lot 'lighter' of an interface than the frustration of paging. (that's my own opinion, not backed up by any usability studies)

just like people expect from a chat room.

In something like Twitter or Identica, messages are largely unrelated to each other, therefore the unit of individual context is a message, and the newest messages appear at the top.

In something like IRC, messages tend to be very heavily interrelated, and the unit of individual context is the entire channel - or at least the past five or ten minutes. Until IRC clients learn to split channel contents by semantic context, they present the entire context (i.e. channel history) in chronological order for your perusal.

In something like email, messages tend to be somewhat interrelated, but because each message has links to its related messages, it's easy to break up a mailbox into threads. Generally, I would expect this kind of system to show the newest thread at the top, but the individual messages in that thread chronologically.

Since some email threads grow to enormous lengths, it's not always useful to have the first two thirds of the page occupied by messages posted a month ago, when all the activity is occurring in the leaves. In this situation, it might be useful to only construct threads based on activity in the past week or so - that way, the individual sub-threads of the Monster Thread can take their appropriate places among any other threads that have occurred recently.

Personally I quite like Facebook's hybrid reverse chronological order and box at the top for discrete updates with responses to those updates ordered chronologically and updated inline.

http://activitystrea.ms/

It has a lot of idiosyncrasies. One thing I noticed recently, and tweeted about, was how Facebook uses different ordering within a single view of its News Feed:

> facebook stream format: <(>>>)<(>>>)<(>>>) (reverse chronological order for news items; chronological order for comments on news items)

http://twitter.com/#!/BenATkin/status/10561264480686082

  A: Because it messes up the order in which people normally read text.
  Q: Why is top-posting such a bad thing?
  A: Top-posting.
  Q: What is the most annoying thing in e-mail?

True, most other live-chats do the reverse. But Twitter, blogs, and feeds are training people to read upward – it's the layout with momentum.

The old way was dictated by handwriting and then typewriters; it's no longer required with most written communication keyed-in. Even where a physical reason may exist to prefer a text entry box near the keyboard, as on smartphones, it's still easy enough to compose-at-top (as evidenced by URL bars and search boxes). Or, a covering animation could cause messages to visually 'whoosh' from bottom-entry-area to latest-on-top upon send.

I expect at some point a tipping point will be reached – perhaps as a generational thing, or when some other post-Twitter channel takes off – after which even older interfaces will flip. (Is there an IRC client that's latest-on-top yet? If not, I expect one soon.)

Eventually, even prose that seeks to create a strong sense of time-falling-in-from-the-top may reverse its usual line-ordering.

a) my service won't really stand out in this respect, which may be fine, and

b) the box will be at the bottom, which means the human brain will have to look for it in a variable place, causing far less people to use it than if it was in a fixed place on top -- and causing less initial engagement with the site.

If you notice, youtube did whatever they could to get popular in the beginning, and it worked for them. They were one of the first web 2.0 companies to be sold for above a billion dollars.

Anyway, back to my point ... if you read email (not in gmail, but in regular email clients) then you usually have conversations in reverse chronological order. Come to think of it, I always feel I have to remind people to "read from the bottom" when I forward an email thread. So perhaps it doesn't lend itself to the best experience.

This seems to suggest that the best experience is indeed: bar on the bottom, infinite scroll going up (or pagination going backwards).

But now I will have the problem of drawing the user's eye to the bottom of the screen. Most chats will initially be empty, so I will just have a large empty space on the top, and a chat textbox on the bottom. What about that? Fine for IRC but not for a website, I think.

I think it is:

1) keyboards on phones are on the bottom, so as not to obscure our view of the screen, and we want that textbox to be in line with the keyboard

2) we read from top to bottom, so it is more natural to continue reading this way inter-message and not just intra-message

But there is one BIG ONE that seems to really scream "newest on top" for me:

On the web, things start at the top

This makes sense, because they are documents. And as such, embedding chat in a document seems to demand a large empty space: most of the important site elements (header, etc.) will be on the top, and to see the input box you have to look all the way DOWN.

Maybe I just need to come up with an idea to draw the eye there and make people want to type. But what?

about this

I have strong feelings