In jsonl a modified chunk will lose you at most the removed lines and the two adjacent ones (unless the noise is randomly valid json), in particular a single byte edit can destry at most 2 lines.

utf-8 is also similarly self-correcting and so is html and many media formats.

My point was that in my made-up concatenated json format

[]"""[][][][][][][][][][][]"""[]

and

[]""[][][][][][][][][][][]""[]

are both valid but have differ only for 2 bytes but have entirely different structures.

Also it is a made-up format nobody uses (if somebody were to want this they would likely disallow strings at the root level).