There absolutely have been exoduses from reddit before, and many of the resulting sites still exist.
However, in general, these were driven by Reddit banning some sort of abhorrent content, so they were kinda self-limiting; few normal people would want to use a reddit clone that was 90% populated with the denizens of r/fatpeoplehate or the upskirt people or whatever other sort of horrible weirdos were impacted by reddit's bans.
This is really pretty different, in that it impacts the average user (or at least the average power user) so might potentially lead to more reasonable breakaway communities.
However, in general, these were driven by Reddit banning some sort of abhorrent content, so they were kinda self-limiting; few normal people would want to use a reddit clone that was 90% populated with the denizens of r/fatpeoplehate or the upskirt people or whatever other sort of horrible weirdos were impacted by reddit's bans.
This is really pretty different, in that it impacts the average user (or at least the average power user) so might potentially lead to more reasonable breakaway communities.