@Zayedsakib had answered this question so I won't repeat it..

However I do like to stress that posts and comments don't actually get deleted on the Steem Blockchain, when you are editing a post/comment on Steemit, what you are actually doing on the blockchain level is to "overwrite" the comment and have Steemit show the new comment instead of the older one.

In fact even your upvotes and flags are registered on the blockchain the same way if there is any changes.. that is why you don't get your Voting Power back when you cancel a vote.

Accessing to any of the Steem blockchain explorer and you can see all of it.

Imagine you can leave a "hidden message" on the Steem Blockchain by editing it as soon as your posts gets registered on the block.