Ok, I've checked all the nightlies from r904 down to r740 as well as r534, r380 and r239. It does the same thing in every single one of them.
I've attached one more picture - the exit string is displayed in several colors, and when you move the window those colors change.
The relevant strings are
// 00CA - \90Are you sure you want to abandon this game and quit to DOS ?
"\U00DE\UE090Opravdu chcete ukončit hru a vrátit se do Windows?" 00
// 00C5 - \98\ad
// 00C6 - \89\ad