How the 4chan crowd interacted with it. That seems hard to test beforehand.
First, no, not hard to test. Second, the 4chan response is entirely predictable.
A Youtube guy, Sargon of Akkad, had an analysis of previous interactive internet promo screwups. A long list. I hadn't heard of them. Microsoft should be in the business of knowing such things.
https://youtu.be/Tv74KIs8I7A?t=14m24s
History should have been enough of an indicator if they couldn't be bothered to do any actual Enemy Team modeling on different populations on the internet that might like to fuck with them.
http://www.wired.com/2016/03/fault-microsofts-teen-ai-turned-jerk/
Could this be a lesson for future AIs? The AI control problem?
[future AIs may be shutdown, and matyred..]