my kudos to you for being able to track down an issue like that. the hardest ones are the ones where the difference is something so slight, hard to see.
so the lesson to be learned here by other plugin devs is to carefully check to see that you are implementing true unicode all the way through the process, and not something less than that, right? (it almost sounds like a music traders nightmare of an analog stage somewhere in the distribution tree
how would you phrase it to other devs, or is what you have already said enough? (meaning, to warn them from making the same mistakes?)