I would imagine that this would be pretty difficult to fix for the stated reason:
Since I don’t believe there would be an easy “look up” system to attach the old links to the new threads (unless there’s some sort of internal metadata attached to them)
The ship has long sailed on this one unfortunately. I don’t think we can afford to invest effort into this, the impact would be too low and the mapping would not be complete or very difficult to complete. The IDs of threads have changed since we moved from Kunena forum to Discourse in 2015.
If any official posts have outdated links you want corrected, let us know.