I don't think there is a good or even a realistic way to implement this. Pure text can't really hide anything and what we are writing here is really pure text with all the code bare.
And even if we were using visual editors, as long as you know there is some hidden meta information or formating with a piece of text you want to plagarise, you just paste it into a piece of editing software that doesn't support nothing but text like notepad and then copy what you have there which would be just the text you see and nothing hidden.
If protecting your content like that was somehow possible, all websites would be implementing it, not just steemit.