It dropped without warning on my Win11Pro Surface Pro 11 and my wife's Win10Home LG 17, and it was IMMEDIATELY popping up in everything we were doing like a damn VIRUS (copy and paste help; do you want me to rewrite that for you; here are your past options; let me show you how to make a reminder from that calendar entry). It makes me want CLIPPY BACK.
I SWEAR ON MY RIGHT TO EVEN OWN A COMPUTER - if I can't bury Copilot on BOTH our computers, I will leave Windows forever. This is infuriating, and I should have just written I AM LEAVING WINDOWS because everything I read last night indicates this is just the tip of the iceberg to monetize the $19 BILLION they have already spent and the $80 BILLION they recently announced.
UPDATE (before I even publish since I started this post last night) - I tried various setting changes; registry edits; even group policy tricks, and that stupid-@$$ Copilot squiggle is still there on every new Word document.
UPDATE 2 (post-publishing) GPEdit did no good again, and no account setting within any of the 365 apps to turn it off, BECAUSE IT IS A D@MN WEED AND IT ADMITS IT (from Ask in the Copilot App):

I've been just ignoring it (mostly) and I don't find it overly intrusive (so far)...
Like @nntheemperor , I want to see if I can just live with it...