> If the file extension is .txt, I always expect it to be opened as plain text. The file extension is, rightly or wrongly[0], the metadata declaring the file ty

> If the file extension is .txt, I always expect it to be opened as plain text. The file extension is, rightly or wrongly[0], the metadata declaring the file type — nobody would consider it reasonable for an .exe to remain executable if the extension is changed to .txt, after all. That statement is quite wrong and shows a good dose of ignorance. To start off in UNIX systems the extension means nothing regarding whether a file is an executable or not. All it takes is a +x flag and a file format (header, magic number) that can be executed. Also, file extensions mean nothing. In fact, a popular and very basic trick to fool clueless users to run malware (and one which any anti-malware tool checks) is to sneak executables with a different extension, because it only means something to clueless users. And a file with a txt file extensions means nothing at all. The only thing that matters is the file content and it's file permissions.