[lesserknowndan]

What do you mean? Preview your own comment?.. Preview someone else's comment?..

Do you mean that as I am typing this comment I might press a preview button to show me this text that is already right here in this text input?..

I don't mean to pick on the asker, but why is it that these days so many people posting to Ask HN just write a few words and then expect everyone to fully understand what they mean?!