https://steemit.com/witness-category/@timcliff/timcliff-s-updated-witness-application
팀클리프 증인의 말에 의하면..SNS트랜잭젼과 Banking트랜잭션을 구분하지 않고.. 3초마다 생성되는 하나의 블록체인에다가 기록하는 군요..--;; 그럼 7일전 까지 수정 가능한 원리는 수정된 포스팅이나 댓글을 별도의 새로운 트랜잭션으로 보고 새로운 블록에 기록하는 것 뿐인 것 같내요..

"Witnesses are tasked with validating and producing the blocks for the blockchain, which ensures everything in the network operates smoothly and correctly. Every three seconds one of the witnesses assemble all of the transactions that have occurred (such as posts, comments, votes, STEEM/SBD transfers) into a "block" and then they store all that information in the distributed database network called the "blockchain"."