I came over from here, as the original question has changed.
This question is probably for Florian at first: is it possible to have an option at mpeg tag writing, as ID3v2.3 with ISO-8859-2?
As I wrote in the previous tread, it would not probably breach the standards that much, as Latin-1 and Latin-2 are very similar, just a few characters differ, all codes above 127.
What happens now, if I choose writing in v2.3/ISO-8859-1 is that as soon as I save my files, those four characters missing from the ISO set are immediately replaced with o/O and u/U, not only in the tags, but also as they appear on the user interface of Mp3tag too.
My current workaround for this goes like this: first I write tags with Mp3tag using v2.3/ISO-8859-1, that is appropriate for a good majority of the cases, then I correct the rest in WMP, that seems to write back the needed characters in the v2.3 tag properly.
However, as it was pointed out that WMP might do some "proprietary stuff" in the background, I would like to stick with Mp3tag exclusively, and avoid this "hassle".