Meno – what if someone realizes that what they wrote was L”H or onaas devarim or tmi?
In real life, your words aren’t posted online for the entire world to read for all eternity.
Of course people need to learn to be careful about what they write and say, but realistically, they aren’t – that’s why we have a concept of teshuva, and that’s why we want to limit the potential damage that can be done.