BIP 50 describes the temporary steps taken to correct a chain split in March 2013. One of them was:
Limit the maximum block-size created to 500,000 bytes
I've seen this commit, but it doesn't address block size limit:
What was the actual commit that lowered the block size limit? Did the update merely adjust the soft limit miners use when generating blocks, or did it actually cause nodes to reject relayed blocks larger than 500K?
I think this may be relevant because if the latter is the case, it would represent a precedent for raising the block size limit. The limit was later automatically lifted (apparently).