André Hentschel pointed me to a strange cmdlg32 resource string:
IDS_ABOUTBOX "&About FolderPicker Test"
The text seems unlikely to be correct. IDS_ABOUTBOX was introduced in 87b81de0 but was not used even in that patch and as far as I can see it is still not used by Wine. Looking at the Windows comdlg32 dll I see no string resource (but that mostly make me suspicious of the tool I used).
Furthermore, none of the other strings in that string table seem to be used either: IDS_DOCUMENTFOLDERS "Document Folders" IDS_PERSONAL "My Documents" IDS_FAVORITES "My Favorites" IDS_PATH "System Path" IDS_DESKTOP "#msgctxt#display name#Desktop" IDS_FONTS "Fonts" IDS_MYCOMPUTER "My Computer"