Instead of appending a random number and writing a primitive hashing function for it, why not just add a count to the title and increment it? It would make more sense for the URL, though it may be slightly more work. So instead of typo-post, typo-post_5351, and typo-post_3425, you would get typo-post, typo-post_1, and typo-post_2. btw, the maintainers will almost certainly not add this patch to trunk as it will probably be considered too remote a problem to worry about.

I'm surprised we don't have a date scoped uniqueness constraint on permalinks already. But, on reflection, that might not be all that easy to implement...