I think this is a bug.
On JCloze files, using Meier's find and correct script and quite possibly on all regular cloze files where hint has been enabled, I get "The Next Letter has been added" as a feedback item. I have been removing that message from the config file so as not to confuse the students. I thought I would report this.
I hope to attach an image here that demonstrates the issue. If this forum is not the best place to post an item like this, please let me know.