Multiple problems with so-called "SEO" (and it's been pointed out multiple times, just do a search here and at Area51).
1. phpBB is dynamic by nature (as is pretty much ALL
bulletin bard software). URLs going to be dynamic no matter what. You'll always have to store a forum_id/topic_id/post_id.
2. You'll still get duplicate URLs if the topic title is changed. Before you say "well this can be solved by adding the topic_id", that's no different than how phpBB currently does it.
Honestly, I don't see why people make such a big fuss about this. phpBB is already "SEO friendly". If it wasn't then why does a Google search for submit_post
pop up with topic titles when phpBB uses dynamic URLs?
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