We will never know what is the literal truth, or what is to be taken on faith unless we have a preconceived opinion. There are those who argue for every word being literally true and havng no further meaning. I simply don’t know. What I do know is that this is a great story and also a parable! Why isn’t the John out there? Great question. How do you refute the death penalty argument and still support justice? Jesus here is a great advocate without using trick arguments and speaking directly to the innermost thoughts of the persecutors. And he is caring and forgiving. But how dramatic is this: a sinner (which we all are to each other) is threatened with death by her accusers. Only Jesus stands between her and a humiliating death from the mob. Jesus intervenes quietly and changes the hearts and minds of the accusers. In the end (as in all our ends) she and Jesus are alone and he forgives her. Beautiful story. Told in about 10 sentences too. I am getting so sentimental in my dottage!
“Kilroy was here.” 
I’d just like to point out that the authenticity of this passage has been considered at best dubious for at least a century. It doesn’t appear in either the Codex Vatanicus or the Codex Sinaiticus, both 4th century. It first appears in the Codex Bezae (6th century). In later manuscripts, it is in different locations, not always even in John. Normally it was included but added in brackets or subscript. IIRC the passage was apparently not even commonly included in the main text of Bibles until the ‘Revised Standard Version’ in the Sixties.
As I recall, it was “GORILLAZ RULEZ!” but I don’t have a cite handy.
“W.W.I.D.”
The nuns at St. Mary’s always tol us that he was writing the sins of those around him. That sort of makes sense, since when he then says “let he among you who is without sin cast the first stone” it would make his point more clear.
The Pelican Bible Commentary for John, written by John Marsh, sidesteps the issue wildly, findiung it more important that he bent down than that he actually wrote, and challenging the use of th verb to mean “write”. He seems to hold that the sin, like the writing in the dust, is impermanent, and can be swept clean.
Marsh’s book also points out, as has been noted above, that this section is suspect. It doesn’t appear in any of the early Greek uncial manuscripts, except for one. For the first thousand years of Christianity no Greek commentato even mentions this story. The language differs from that in the rest of the Gospel of John. The nuns at St. Mary’s never mentioned any of this stuff to us.
What was he writing with?
Maybe he was just “writing” his name! 
I reckon he wrote the 1st-century Hebrew equivalent of “sauce for the goose” or “it takes two to tango”.
He was writing down the names of the accusers! Thats my take on it anyway.
The previous day was the last day of the Feast of Tabernacles, something like a week long Thasnksgiving. since this episode supposedly took place “the next day” we are dealing with an incident on the Sabbath when the law prohibits writing except with dust. This supposedly is Jesus demonstrating his familiarity with the law which may have only been known by learned scholars (pharisees) but long since abandoned as a practise amongst the general population.
Now what is even more interesting is this prophecy written several hundred years earlier
And indeed these scholars turned away, led by older ones , supposedly wiser ones.
So once again we have the contempt that Jesus had for those who boasted in their knowledge and practise of the law, yet failed to recognise the significance of his overt actions. For all of us we have the demonstration of another fulfillment of prophecy.
The word “eikonoklastes”! His prophecy of me.
It’s in my old King James version.
In the main text in the same type face, no brackets etc?
(I could be wrong, it’s been known to happen before)
“Ain’t Nobody’s Business if She Do”
For some reason, I rememeber Peter McWilliams referencing this very story in that fantastic book of his.
This is one of the things that the passage brings home so strongly - the punishment for adultery was for both man and woman to be put to death:
In this story it is clear that the “The teachers of the law and the Pharisees” were not really as interested in seeing justice done as they were in trying to trap Jesus in an ethical dilemma. (My guess is that the man was there in the crowd, being protected by his cronies.) I am sure that Jesus was well aware that it was a trap for him and he dealt with the situation superbly - balancing mercy and justice in a way that is a challenge to us all.
My bible has it as a footnote that some earlier texts do not include this story - it would be very sad if it were not authentic!!
Gp
“Whom this reads is mad”
“Just go here and turn left at this building. It’s a temple. You’ll follow the road this way about two blocks and you’re there.”
As with Moses, Isiah, (and others), Jesus could do some pretty astounding things; things at great variance with “conventional physics”.
Jesus wrote a practical implementation of his oft-taught “As you measure, so, too, shall you be measured.” or “As you judge, so shall you, too, be judged.”
The older dudes were, as usual, the wiser dudes and put their clothes back on (–“took their judicial nakedness off”–) and departed the AO.