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Yes, but the flag would still be registered on the blockchain, its permanent regardless of what the actions are in the frontend (after flagging).

I am not sure if I follow you , in my understanding whatever damage a flag causes can be undone as soon as it is removed...

am I wrong ?

Not from my understanding of how the blockchain works. Each vote is permanent regardless if you "unvote". Just like each post you make is permanent, regardless if you edit, all you're doing is just updating the frontend content, but all the previous data is still registered on the blockchain.

If that is the case, you are right flagging won't help in that sense...

It would help, it just really needs to be careful about who it affects, cuz getting downvoted by whales hurt.

The permanence of data on the blockchain isn't inherently a problem, it depends on how it's used. For instance, a 1BTC deposit is permanent, but a 1BTC withdrawal still means the account has, after the withdrawal, 0BTC.

So it seems here that the presence of the vote, in the ledger history, is not inherently a bad thing as long as there's a means to unvote it, AND that the unvote actually does something meaningful. That is, if it undoes demonetization, has the appropriate counter effect to reputation systems, etc.

Now, I don't know steem based platforms well enough to know if these effects are part of it, but were they to be, then immutable block chain data wouldn't be a problem.