Hi Andreas,
> The version of fsck that this project implements does not have any repair functionality, and as I understand it, this is by design.
It's mostly because of the lack of manpower. Currently libexfat performs some base checks of on-disk structures while it reads directories and files. Fsck just uses this side-effect. Obviously fsck needs another approach to be able to repair FS. It's quite complex and interesting task.
> Are there any plans to implement such functionality?
Not in the foreseeable future I'm afraid. I'm very busy now.
> Are there any reasons not to implement them?
The only reason I see is possible incompleteness of my knowledge about exFAT. Since all info had been obtained using reverse engineering it's hardly possible to guarantee that this info is complete.