If preview were the initial default then you don't need the preview checkbox, just a single button labelled "Preview Message" with two buttons at the preview page for further Preview and Submit. I must admit I like the idea of two buttons rather than a Submit button and a checkbox.

I would be happy with either, though that suggestion has two drawbacks:

- it would take a lot more programming (up to Max to decide if it's too much)

- it enforces the same policy on everyone (which is bound to make some people unhappy; my original suggestion leaves the read/post user interface looking exactly as it does now if you don't want to use the feature).