“Why not use some part of the unique ID of the post, like with NNF. I won't know what this post's ID will be until I've posted it. The previous post by theraje has an ID of #12vskt7akvvk, since this is base-36 (0-9 / A-Z), one could use some simple pattern to decide what the roll was, like "the first number in the ID", or the first letter A-T (20 letters). ”

Because I'm not a web developer, and rely on the work of lots of talented people who deal for me with browser inconsistencies, SQL injections, hosting hell, etc... :) The phpBB forum which I use does not expose randomly generated unique IDs publicly, though it's well possible that it uses some form of them internally. For more courageous people, that could be an idea though...