Is the Ext3 filename limited to 255 symbols or 255 bytes?

I cannot save the file with the name containing more than 127 Cyrillic UTF-8 symbols on my Ext3 filesystem. It is possible so save the files containing up to 255 English UTF-8 symbols though.

So is there a limit on a number of bytes containing the file name or the number of characters in the file name? In case of the former, one would expect even more strict limit on the file name length in Chinese, for example. Is that right?

Yes, the maximal file name length is 255 bytes, resulting in varying max length for filenames depending on code points used and their encoding length.