Is this something to be worried about? Does it potentially impact other CryptoNote coins or just Boolberry?
All they are saying there is that if you want to prune the signature data, you need to still keep a hash of the signature data in the chain of hashes (of Merkle trees) for the blocks. In other words, you need to still be able to prove which signature signed which transaction, even if you've actually discarded the signature data.
I believe BBR already does the correct thing. And afaik, Monero does not discard signature data, but I could be wrong about that. If they do, I assume they would do the right thing as well.
BBR does not include a hash of the signature data in the blockchain. I'm not sure what exactly are the alleged vulnerabilities either, but I've always been uncomfortable with it, as I said way back in the 2014 BCX free-for-all thread.
Monero does not have any kind of segregated witness so no issue there.