If I just went with whatever AI praised, I would have stopped at AGAIN.
The reason I gather these opinions is more as brainstorming, to see what points are brought up. It adds to the discourse. And what's great about it is just how fast the turnaround is in these discussions--they're almost as prolific as I am. 
As this case demonstrates, ultimately I make the calls--based on real examples and what works in practice.
INSIST is a winner here
And I think we can see why if there's an arity-1 variant that uses the word UNTIL and is intended to be used in this way, it would need to be LOOP-UNTIL to make sense.
append data until [any [request-server-token, wait 5]]
Even a religious Rebol2/Red zealot would have a hard time not reading that as postfix (if they speak English). It's as if the APPEND itself is looping.
Or not! Oh well, better luck next time... 
But of course, someone could say until: insist/ in their standard utility include file, and define other things however they want. Freedom of choice!