How do I create hidden characters in a .txt file?

Does anybody know how? I'm talking only plain text, not text hidden in a Word document.

I've heard of Notepad ++ but have had no experience with it.

Thanks

Why do you want to do this?

I just want to know if it can be done. Do you know if it can?

To the best of my knowledge, no.

Although there may be a zero-width unicode character.
It's possible that there is a better way to do what you want to do, but first we need to know why so we can tell you that better way.

I'm not sure what you mean by "hidden characters." I've never heard of it? What process would need to be done to ensure that only you or someone you trust could see the characters? You could encrypt the file using Kleopatra, it works great.

Well the problem is this. At a certain unnamed website, I've had to create three different accounts in the last 60 days because a troll keeps hijacking my username and has logged into an account using my name. Complaints to the administrators about it have been ignored so I suspect he's either cracked my password (which was somewhat unique) or is using my username but adding hidden characters to it to fool the website into thinking it's a different username. Changing my password doesn't seem to have helped.

I need to come up with some kind of plausible proof of what's going on here since my requests have either been ignored or they're saying nothing's wrong.

It's ridiculous. Has anybody encountered this kind of situation before?