Can watermarking Unicode text using invisible differences sneak through Emacs, or can Emacs detect it?

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

There is a thread now about confusables.

I read this,

   Unicode allows user tracking by means of invisible text marking. Any
   string can be converted into its binary form and then recoded into a
   string of zero-width characters, which can then be invisibly inserted
   into the text. If the text is posted elsewhere, the zero-width
   character string can be extracted and the process reversed to figure
   out the identity of the person who copied it.

which seems ot be about a special case of confusables, and it makes me
wonder whether Emacs does, or could, show users when Unicode confusion
occurs, or prevent or fix it somehow.

First, is that issue of invisible characters real?

Second, does Emacs do anything now such that these tricks
won't succeed?

If the problem exists in Emacs now, could we prevent it?  I see a few
ways to try.  I don't know whether they would work well.

* Indicate the different encodings on the screen somehow.

* Canonicalize such seqences (perhaps when reading text into Emacs),
so that different encodings of the same text become identical.

* Use a stand-alone canonicalizer program.

-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)