TLDR: Karbo made a novel and unique protection against 51%-attacks which disallows cancelling transactions from blockchain during reorganization. Now Karbo network nodes will refuse to reorganize to an alternative chain until any transaction from the current public chain is missing in the alternative chain. Even more, the alternative chain has to win within 10 blocks.
I like your modesty - "novel and unique protection against 51%-attacks"
In fact, you just borrowed 3 lines of source code from Soldo project - yes, this "novel and unique protection against 51%-attacks" is so silly simple;-)
I know it for sure, it's my code