I don't see how that's a security flaw.

Steemit is about freedom of expression, IMO. That includes comments on other people's posts. While the ability to "delete" posts (note that you cannot really delete anything from the blockchain anyway) might seem desirable as a means to handle the troll problem, if it exists, this is essentially a means for censorship.

The best defense against a troll is to ignore it. If you try to silence it it will only come back with a vengeance.
The best defense against a stupid comment is a better argument.

Censorship is unnecessary and counterproductive.