Hi everyone. Here's an update on the old forum content:
I attempted a test migration over the weekend, to help surface any potential issues with the data restoration.
It turns out my original pessimism was warranted. The migration is messier and more difficult than I was beginning to think. But, with that said, I do believe that salvaging the old forum content is possible. I've spent many hours already ironing out the kinks and I am planning a real migration attempt sometime this week or possibly over the weekend.
The main question is how clean will the restored content be. The hardest part of this migration is faithfully restoring those parts of the posts that most of us don't think about, things like formatting, quoting, links, images, likes, etc. All of those are handled in a completely different way in the old forum compared to this new system. Without a delicate transformation of old forum posts to new forum posts, some content may not be rendered accurately (although all text should be readable).
At minimum, I believe I can restore all textual content from the previous forum. But, currently I'm uncertain whether I can preserve some of those other parts. Depending on how it goes, the restored posts may contain broken links, images, emojis, or extraneous BBCode markup tags.
I can't promise perfection, but I'll try my best to restore the old content with minimal formatting issues.