Last night I spoke at length with Ivan Krstić, the head of information architecture for the One Laptop per Child project. He wants to reach an agreement with us on a common markup syntax as they are currently researching the OLPC document format syntax and we noticed that by pure chance our syntax for unordered lists, ordered lists, bold and italics is already identical. They have tentatively agreed to change their link format to match ours.
We have agreed to be more tolerant with headers so that equal signs after the header would be acceptable and if the left and right side have a different number of equals signs, then the left side would determine the size. Also, considering that MediaWiki does not allow a single equal sign for a header, I would argue that we should not either and that level one headers (the largest) begin with two equal signs. We have also agreed that transclusion is too complicated for a simple markup like Creole and are looking at which markup would be best to display images.
Between the OLPC and Creole groups, we are now researching to see what would be the best markup for a horizontal ruler and preformatted/monospace text. I am also making a page Comparison with OLPC markup to help speed the process.