When students try to evade plagiarism detectors, they will swap characters like replacing spaces with nonbreaking spaces, replacing letters with lookalikes (I vs extended Cyrillic Ӏ etc), and inserting things like the invisible 'Combining Grapheme Joiner'
IMHO it isn't a feasible way of watermarking text though - as someone would promptly come up with a website that undid such substitutions.
> IMHO it isn't a feasible way of watermarking text though - as someone would promptly come up with a website that undid such substitutions.
It doesn't matter since there's no one-pass solution to counterfeiting.
You have the right of it-- the best you can hope for is adding more complexity to the product, which adds steps to their workflow and increases the chances of the counterfeiter overlooking any particular detail that you know to look for.
IMHO it isn't a feasible way of watermarking text though - as someone would promptly come up with a website that undid such substitutions.