I know what "plain text" is and even so, it can contain identifiable markers, if you want to track down a leak let's say.
"Something đť—Śomething will launched on Novemá–Żer 3rd"
This "plain text" string has two markers that aren't actually ascii, `đť—Ś` and `á–Ż`. By changing the markers for each person you send it, you might be able to track down who is leaking things, if they're careless and just copy-paste stuff that look like plaintext but actually isn't.
"Something đť—Śomething will launched on Novemá–Żer 3rd"
This "plain text" string has two markers that aren't actually ascii, `đť—Ś` and `á–Ż`. By changing the markers for each person you send it, you might be able to track down who is leaking things, if they're careless and just copy-paste stuff that look like plaintext but actually isn't.
Anything that is a homoglyph (https://en.wikipedia.org/wiki/Homoglyph) can be used in this manner