Cis didn't originate from gender. Cislunar, cisalpine, etc.

And it's ok for you to not identify as cis. You get to have whatever identity you want.

We are discussing a platform that censors discussion when that discussion includes trans and not trans people. Unless you are X, the platform, I don't think your identity is germane. (And once again, you are valid.)

That isn't justification to censor the term.