Original sentence: Researchers have pointed out that the history of every single bitcoin is registered and publicly available in the block chain ledger, and that some users may refuse to accept bitcoins coming from controversial transactions, which would harm bitcoin's fungibility.Wallets and similar software technically handle bitcoins as equivalent, establishing the basic level of fungibility
Edited sentence: However, the transparency of bitcoin transactions could make bitcoins less fungible than they appear.Researchers have pointed out that since the history of every single bitcoin is publicly available in the block chain ledger, users may refuse to accept bitcoins coming from controversial transactions.Wallets and similar software handle bitcoins as equivalent establishing a basic level of fungibility