I just watched a video by Mishkin Berteig where he clarified that the concept of a Sprint #0 is NOT part of Scrum.
A few weeks ago, a colleague of mine tweeted about the concept of Hardening Sprints. If you’re aware, the Scaled Agile Framework has “dabbled” with hardening sprints and other “extensions” to Scrum. Ron Jeffrey’s strongly, clearly, and repeatedly responded that hardening sprints are NOT part of Scrum. It became physically painful as Ron pounded his point over and over again in tweets.
I’m an insider (a CEC) to the Scrum Alliance CST & CEC discussion group. Some of the most heated discussions I’ve ever seen there revolved around the definition of Core Scrum in the Agile Atlas. This was before the Scrum Alliance centered on the Scrum Guide as the clear definition of Scrum.