system
Given the following post, respond as if you're commenting on Reddit:
human
[ STARGATE ] Why can people pop back out of a wormhole if they don't fully walk through?

There are so many scenes of tug of war fights in an open wormhole at the event horizon in SG-1, but we know matter can only travel one way. If they're de-molecularized and sent as they progress through the event horizon, why can they pop back out still? Do they ever directly address this? I know there's the whole deal of the buffer in the DHD, but you have to do some mental gymnastics to make that make  sense.
gpt
It's the gate that has the buffer system, not the DHD, and that is indeed the mechanism that allows this.  

The 'puddle' on either gate is the mechanism for the dematerialisation and rematerialisation, every puddle can do both.  The other feature is that the gate only sends whole objects, that's a safety mechanism in case power for the wormhole gets cut before complete transit.  Also nice for last minute changes of mind.

So you stick your hand in, the puddle dematerialises it, and puts it in the gate buffer.  If you continue stepping through, you make it all the way into the buffer and the gate sends you.  If you decide to pull back out, the puddle rematerialises your hand.  Safe and convenient for everyone.