I may misunderstand the purpose of this feature, so please keep that in mind.
When viewing threads with some expanded posts, and some collapsed posts, the grey rectangle surrounding the thread doesn't enclose the entire thread. (See screenshot.)
Expected behavior:
If I understand the feature correctly, the grey rectangles are intended to make it easier to follow posts with many replies by visually separating them into their own "threads" on the page. I would expect the grey rectangle to enclose the entire post thread, not only the first few replies.
Screenshot:
http://schend.net/images/screenshots/slashdot/thread_outline.png
Firefox 2.0.0.13 on Windows Vista.
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I believe you are mistaken: those comments do not appear to me to be a child of the expanded parent above, but of that parent's parent (by geekoid). Looks right to me.
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Hm. You're right.
The bug needs to be changed to "grey boxes aren't at the same indentation level as the threads they enclose."
Anybody looking at the screenshot posted to this bug would assume that the comments below the grey box, but tabbed *to the right of it* should be included within that discussion. The indentation is completely throwing me off in this case.
A better solution might be to steal a little detail I noticed on the posting preference page, where the radio button groups have a little grey line on the left-hand side of the page that indicates where the tab group begins and ends. This could easily be adapted to have multiple lines to represent multiple levels of discussion, and I think it would be a lot less confusing than the existing solution. I can mock-up a screenshot if you need one.