The absolute SCORCHER of a set closer in Halley's is overshadowed somewhat by the controversy of Trey's mid-song departure, a la the 10/31/98 Ghost. I was dead center, around the 25th row back. I vaguely recall Trey flashing an annoyed look to his right (stage left), but honestly, it's foggy enough of a memory that I can't be sure whether it's legitimately my own memory, or my lasting mental picture after years of hearing and reading other fans' stories of that moment.
What I do clearly remember is, with his bandmates holding the groove, Trey removed his Languedoc, bowed, and left the stage. Mike and Page exchanged a glance, perhaps laced with a sliver of confusion, but with enough ambiguity as to admire the quality of their poker faces. The jam faded out, the remaining three band members exited stage right, and then shortly afterward the four of them returned uneventfully for the last two songs of 1.0 I'd see them play.
To use the parlance of our times, the level of "ripcording" in Trey's sudden departure has been built up way too much over the twelve-plus years since that show. Relistening to the Halley's jam today, I was surprised to hear them turn the heat down to a simmer a good minute or two before Trey exits, making the fade out sound absolutely natural. Given the rumors swirling about the details of the impending hiatus at the time, and with the 10/31/98 Ghost in recent memory (a far more jarring end to a jam than this one), I think it's very likely that fans perceived drama that did not exist. I'd be interested in other attendees of this show sharing their memories of this moment.
I'm not particularly huge on watching video of past Phish shows (as opposed to merely listening to the audio), but for several reasons, this is one show I'd absolutely love to see again someday.