Reporting read-only files
For some weird reason, some of my track files were marked as read-only. This meant Bliss could not update missing ID3v2 tags, but it didn't report the problem either. Once I found the problem (as reported by J River Media Center) I managed to use Bliss to fix the tracks successfully.
Obviously this should also be reported better! Was it not in the Activity page?
Just the activity page might not be enough though; I sometimes think there's a category of error which you ought to be alerted to more proactively.