With http://github.com/fieldtrip/fieldtrip we are using jsonlab in the data2bids function. @DidiLamers identified a problem when converting a dataset with an author (which goes in the dataset_description.json) that had a non-ascii character in her name (in fact, it was the letter "í", with an acute accent). The BIDS validator subsequently complained that the json is not UTF8; also opening the json file file in the Atom editor resulted in the character being shown correctly.

It might be that this is solved already in version 2.0; we are now shipping FieldTrip with jsonlab version 1.5.

If the limitation is still there in 2.0, I would like to discuss whether this can be solved on the jsonlab-side.

An alternative that I see is that around https://github.com/fieldtrip/fieldtrip/blob/2a67cb59746eb81fe05bc118c96d5f257a63f51c/data2bids.m#L2208
we introduce some extra code to deal with this, like reading the json file and writing it back with UTF8 encoding.