As I understand it (from previous conversations) the post deletion/moderation is a manual process.
i.e. they can manually hit the button to delete a post or an entire thread.
But looking at your forum history you have 88 pages worth with 36 threads per page, so that’s 3,168ish threads most of which probably have multiple contributions from you.
So that can’t be done manually.
It might be possible to do it via some kind of database query, assuming the interface they use allows that and they have the necessary SQL skill.
But the other point is that would leave 3,168ish threads with broken dialogue and random missing bits. So I can see why they’d be reluctant to do that too.
Sorry to see you go regardless. Ta-ra.