Now, my question is, going into the hike and knowing there's a 75% or greater chance that JP will turn around at Trail Camp...
What would the perception be if he descended alone and something happened to him. Would we be accused of abandoning him or being irresponsible?
Under what circumstances should someone descend with him? There are obvious circumstances (vomiting, mountaineer's foot, etc). But what if he says, 'I have a bad headache?' What if we make it to Trailside Meadow and he decides to turn around b/c the 'AMS headache' hits earlier and harder than normal?
You and your partner JP most likely will have talked about where he is going to turn around. If at the time of turn around he says I would like you to go back with me...you go back. If the says go ahead you go ahead. Ultimately, we are all responsible for our decisions.
When I am by myself, I throttle back what I will attempt. If my written at home itinerary says directly to Mt. Whitney and back...I will not do a side trip to Mt. Muir, etc. I limit myself to trails and off trail things I have done before.
Also, knowing I will be without a partner for mutual assistance, there will be no short cutting clothing, gear or food. This makes for a heavier pack.
As for perception, who cares. That is between you and JP, not you and the comment writers at the Los Angeles Times or your local paper. Most them don't know a hiking trail from the I-405.