In the original script, Childs was human or at least more convincing as one…
CLOSE ON MACREADY
lighting a cigar. His hands are heavily wrapped. He pours
himself a drink.
A puffy white hand, missing two fingers, enters the frame
and whirls a startled MacReady around. It is Childs.
White and black blotches cover his frostbitten face.
CHILDS
Did you kill it?
He looks as weak as MacReady. A beat.
MACREADY
I think so.
CHILDS
What do you mean "you think so?"
Both men speak guardedly and stare at each other suspiciously.
MACREADY
Yeah. I got it.
(refers to Childs'
condition)
Pretty mean frostbite.
Childs steps back, keeping his distance.
He indicates his
puffy white hand.
CHILDS
It'll turn black again soon enough.
Then I guess I'll be losing the whole
thing…
(refers to feet)
…Think my toes are already gone.
MacReady, carrying the bottle and glass, limps over and sits
down behind a gaming table. There is a chess set and several
decks of cards. The two men continue to eye each other.
CHILDS
So you're the only one who made it.
MacReady begins setting up a non-electronic chessboard.
MACREADY
Not the only one.
CHILDS
The fire's got the temperature way
up all over camp… won't last long
though.
MACREADY
Neither will we.
CHILDS
Maybe we should try and fix the
radio… try and get some help.
MACREADY
Maybe we shouldn't.
CHILDS
Then we'll never make it.
MacReady puffs on his cigar. He reveals a small blowtorch
from under the table and places it beside him on top.
MACREADY
Maybe we shouldn't make it.
CHILDS
(beat)
If you're worried about anything,
let's take that blood test of yours.
MACREADY
If we've got any surprises for each
other – we shouldn't be in any
condition to do anything about it.
(beat)
You play chess?
They regard each other for a moment. Childs painfully sits
down across from MacReady.
CHILDS
I guess I'll be learning.
MacReady grins and hands the bottle to Childs. Childs smiles
back and takes a healthy swig.

Exactly. It's like he already knew. Furthermore, he wasn't hostile like he usually is with MacGready. Cuz remember, before the split to give the doctor the rest, Childs was still suspicious of MacGready. So why the personality change???
Put a muzzle on Tits Malone, PI

When "Childs" reunites with MacReady at the end, he doesn't ask him why the entire camp got blown up.

Carpenter said on at least 1 interview I am aware of, post digital netwotk, that he deliberately left the finale open.

Good food for thought, nicely interpreted. I think that's part of the beauty of this films ending.so much is left to the imagination.

I used to think so, but now I don't know anymore. Was he infected or eatan by Thing and then replicated? Why are the coats and boots so messed up for those two eerie tracking shots of the hallway and Childs' position? If it was just one coat missing, then I'd say Childs was definitely duplicated, but the coats are just all over the place compared to the previous shot. Was it a continuity error and hiw did is slip by Carpenter in editing and post-production, considering it's probably meant to be a key clue. Why the goof?
In all the brutal honesty, Carpenter sacrificed a lot of of logic, continuity and "rules" in order to create paranoia and dread. The fact there's so many theories, options and schools of thoughts on various topics and details means some things simply don't add up. The fact that even after 34 years we know jackcrap is the result of both careful writing/directing/editing and deliberate omissions where (IMO) Carpenter just said beep it" during the editing and post-production.
TLDR, it's still one of my very favorite films ever simply due to the unmatched isolation terror atmosphere, but it's not some high-end masterpiece where just about every puzzle is carefuly put there.