I assume that he’s comparing the migration of Digg users to Reddit when Digg rolled out its very unpopular v4 interface to Reddit making the current changes to their policies today.

https://en.wikipedia.org/wiki/User_revolt#Digg_v4_revolt_and_migration_to_Reddit

In the past, Reddit has cited not wanting to be in Digg’s shoes as a reason for keeping around the old.reddit.com interface for users who did not like the new one, so not wanting to do a Digg v4 is a consideration that I believe has been on the minds of the company in past years.