Polish diacritics are: ą ć ę ł ń ó ś ź ż (uppercase: Ą Ć Ę Ł Ń Ó Ś Ź Ż). They are all separate letters.

By the way, many people think that the Polish alphabet [1] is just English with diacritics, but in reality neither q, nor v, nor x are part of it.

[1] https://en.wikipedia.org/wiki/Polish_alphabet

Some languages have interesting variations on S, C, O and Z (there might be more, I'm not a keen linguist). However, the accents are not always the same. I also believe that nobody has "ğ/Ğ", and I'm pretty sure that nobody has "ı/İ" pair.

The second one wreaks havoc on many, many systems. e.g.: It was breaking Kodi completely (https://github.com/xbmc/xbmc/issues/19883#issuecomment-86833...), and I have personally wrapped many software packages with locale change scripts to make them run.

For more information: https://blog.codinghorror.com/whats-wrong-with-turkey/