This has happened once before and they reversed it. But they said this last time too:
The discussions that have happened in various threads on Lemmy make it very clear that removing the communites before we announced our intent to remove them is not the level of transparency the community expects, and that as stewards of this community we need to be extremely transparent before we do this again in the future as well as make sure that we get feedback around what the planned changes are, because lemmy.world is yours as much as it is ours.
This will be the third time I will have lost all my comment history and have to recreate my large block list. It’s not just a flip of the switch.
Lemmy now has export/import for settings, including blocklist.
Suscriptions and block liste are transferred in two clicks via the settings. For jour history just mention the other account in jour bio.