Yes. They call this excision[0] and it leaves an Audi table hole in the timeline which lets you attach metadata like why there is missing data while still removing the data.
That is certainly something an add-on or external tool could provide.
Immutable is only immutable if you don't have write access to the lowest layer of storage.
It's difficult to implement this by hand, though. What you'll have in storage are encoded blobs of chunks of some kind of sorted set tree structure. So if you are to poke the data directly like that, I would assume it is much easier to just do an offline backup and a restore, and filter the data in the restore process somehow, which I believe is possible.