The block that divided software versions
Bitcoin 0.8 used a different database from 0.7 and could process a block with an unusually large number of transaction inputs. Many older nodes hit a database-lock limit and rejected it, although developers had not intended a protocol change.
Some miners extended the 0.8 branch while others followed 0.7. Until one branch prevailed, the same coins could have different recent histories and payments faced higher reorganisation risk.
Why the older branch won
Developers, mining-pool operators and services coordinated publicly. Major pools temporarily moved back to version 0.7, adding hash rate to the branch accepted by more existing nodes. It accumulated more work and the 0.8 branch was abandoned.
The choice preserved compatibility; it did not mean old software was generally better. Later releases prevented the accidental mismatch from recurring.
Consensus is code plus operation
Consensus rules are executed by real code with databases and resource limits. If implementations disagree about one block, the network no longer has one result.
Human coordination helped restore a common history, but conversation alone did not alter blocks. Miners redirected work and nodes executed rules. The event demonstrates both a social layer and independent technical enforcement.