The message "What Pieter said. Plus not revealing it to the whole world by default doesn't make it unprovable." offers no clear points or topics that could be expanded into a blog post. It seems to reference a previous statement made by someone named Pieter and touches on the concept of proof without public disclosure. However, without additional substance, it's impossible to follow the rules given and craft a multi-paragraph blog post.

For a more effective summary or blog post, please provide a fuller email or content with distinct ideas and information that can be restructured and simplified according to the specified rules.