Technically speaking, even when they flag you, they still cannot delete what you posted on the blockchain. Maybe they affect its visibily on the front ends, but not on the blockchain level.
Once you publish something to the blockchain, it will remain on the blockchain as long as the blockchain exists. And it is not editable. If you edit a post, the original post (and every additional edits) will be visible on the blockchain as long as the blockchain exists.
Another way for the freedom of speech is to have a decentralized website. For example on ZeroNet.
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