I suspect that the API is doing what you are telling it to do which is to populate a field the the value of the field. Instead, you should make a new formula field which combined the existing user list with the new value and then puts that into the field.
The formula would be something like
ToUserList([your existing user list field], ToUserList([Additional User field]))
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Mark Shnier (YQC)
Quick Base Solution Provider
Your Quick Base Coach
http://QuickBaseCoach.commarkshnier2@gmail.com
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