The archaeologists dig and find texts 4 & 5 thousand years old.
The future archaeologist will dig the digital files.
Nothing can really be kept for ever.
Even the blockchain can be abandoned for a newer method in the future.
I believe most of bitcointalk forum messages will be lost, therefore this post is empherial. Even with archivers that work so hard to save every post, in 1000 years, historians won't be able to piece together all the clues.
Blockchain is immutable until people purge stuff they don't like via rollups.
I'm looking for something more immutable than forums, but not quite as distributed as bitcoin.
