> It also writes files in it's own uninterpretable format to object storage, so if you lose the metadata store, you lose your data.

That's so confusing to me I had to read it five times. Are you saying you lose the metadata, or that the underlying data is actually mangled or gone, or merely that you lose the metadata?

One of the greatest features of something like this to me would be the ability to durable even beyond JuiceFS access to my data in a bad situation. Even if JuiceFS totally messes up, my data is still in S3 (and with versioning etc even if juicefs mangles or deletes my data, still). So odd to design this kind of software and lose this property.