Everything beginning 12th February 2019. I'm not sure why it didn't prune everything, and even left some posts untouched in between then and now, but gladly it didn't compromise it all. (Although I'm not sure, I didn't do extensive checking for the whole 4 years after all.)

I tried copypasting them back but it was a bit too much to do manually.

I'm already coding a crossposter but it's hive->steem

That sounds interesting. Although I think on my part the story of Steem is over and it is time to turn over a new leaf.