This is a pixel-perfect mockup, but the image export is a little blurry in places. See source mock.svg for cleaner visuals.
(1). Basic look of talk track on stage top. Messages are small dots ordered from left (past) to right (present). The staged message (if any) is a big dot. There are three time dividers, from left to right:
The placement of the dividers in the mocked up track (above) implies that the discussion shown is young (a matter of weeks, not months) and is still active, with roughly 10 messages having been posted in recent days. If instead all three dividers were positioned left, then the discussion would be even younger and more active:
|||------------------------------ (extremely young and active)
Wheras if all were positioned right, then it would mean the discussion is much older, and has been inactive for at least a year:
------------------------------||| (extremely old and inactive)
If messages are numerous enough to push one or more dividers off stage left, then some age information will be lost.
(2). The track has two cursor modes, "afterglow" and "search". Afterglow mode (aka "talk lighting") is shown above. The cursor is moving leftward and lays a glowing trail on the talk track. It also lays glowing patterns on other tracks, props and the scene to show where the discussion is happening, as described in these posts:
We probably don't need afterglow immediately, but it's mentioned here because we'll need to accomodate it later. We cannot easily combine search and afterglow modes because the search captions (see below) are likely to obscure the afterglow effects outside of the track.
(3). Hovering near stage right reveals a button (above right) that pops a window of auxilliary tools and information (not mocked up here) organized thus:
(4). The cursor in search mode has two captions in tow, each behaving similar to the caption in the poll track (fixed y, towed x, softly fading in and out). The top caption shows the posting age of the message and mnemonics of the message author and difference co-author. (The talk track shows only messages that concern concrete position differences, of course.) The bottom caption is a callout bubble for the message summary. It has a fixed width in em units, but a free floating height. It won't tow beyond the left edge of the track, but stops there.
Image source is mock.svg. Discussion is Interactions of talk track.