I have 2 directories with identically named files. I'm selecting all/some files in one of them, pressing Ctrl+C, going to another directory, pressing Ctrl+V. XnView doesn't ask anything (about existing files and their replacement) and copies new files with "copy" filename suffix added.

Where is standard "File already exists" dialog? Copying files in such conditions using context menu's "Copy to folder" works as expected, and the same with drag&drop copying.