Hi, original author here. Not sure about the issue when whole files are gone but regarding content being deleted inside the files Time Machine doesn't help. The problem is that you won't know which files have been changed. And Time Machine will gradually phase out old backups, only keeping one per week, month, year or whatever the policy is. So at some point the files with your content will be gone and only backups of the files without your content will be stored.

Probably not. Time Machine should protect you against the problem I had unless you purge old backups. I don't think Time Machine ever deletes the one and only version it has of a file.

But dominikmayer has a very good point there in the sibling comment. I think this would only affect files that change though.

No, if you have Time Machine backups your fine (also if you don't have optimize storage - Time Machine may not back up files that aren't locally stored, regardless of sync provider)