That is simply not true. That story has been fed to people over and over since the changes were implemented, mostly by developer sockpuppets I suspect.

If you were here for the past 3 months you would know that those functions worked just fine until they disabled them. It is completely possible for the steemit.com website to display only the last (edited) copy of an entry in the blockchain.

Want proof it works fine? Just go find yourself a old comment without a vote or reply and then delete it. Viola, steemit.com will not display it anymore, just like it should be. If it causes performance problems on the completely separate steem blockchain, that is directly because of questionable development and release practices.
(Que Canned Excuse: It's in beta!)

The complete lack of regard for the user experience around here is depressing, and I tire of arguing with the developers and even supporters for it to get better... Believe whatever you want, if they cave to outside pressure on this issue then I think this horse is probably dead anyway.