In extended mode:
Searching for 'O' works
Searching for\x4F should do the same, but fails
Seearch for \x42 works and finds 'B'
Searching for \x4? finds 'O'
At line 100 in FindReplaceDlg.cpp, in readBase(), replace
current = str[i];
current = str[i] & 0xdf; //to upper
if (current >= 'A') current -= ('A' - '0' + 10);