It's a little unclear what you mean by irreversibly. If you mean in that save file, then yes, like I said if you don't know what you are doing with either a save file editor or a memory editor (trainer), then you can break your save file.

However if you mean irreversibly as in even starting a new game entirely or reloading a previous save from before the modifications, then no. That's actually impossible for either save editing or memory editing to effect because they don't touch any other files.

(Save editing obviously touches the save file that it is editing while memory editing actually doesn't touch any files at all. Memory editing hooks into the memory of a running application and modifies it but the instant the application is restarted memory gets completely reset.)