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...
Somehow I don't mind it as long as I'm not paying for it. I figure I might as well get used to it and put it to good use😉
Showed up in the Android Outlook app and asked to rewrite my email. I let it do it but I had to revert to my original message. However, I found it quite useful in summarizing emails, even ones written in Japanese.
JoeS - I've messed something up here and don't have a button to reply to your comment. Bottom line, to trim it back, do the registry entry; tehn if you have Windows Pro do the group policy edit; and last open Word and do FIle\Options\Copilot\ and check turn off Copilot. Do this last step for each O365 application if Copilot shows up in the left side of the Options menu (only Word and Outlook had Copilot in the menu; the others not).
OOPS - my mistake - when I switched back post order to Oldest I got back the Reply button
Thank you! It's all over my Office install, and I only had the energy to sigh and go on with my work. I'll see if it does anything useful for me, but I suspect I'll scour the web for ways to weed it out of my apps.
JOIN ME IN THIS (UN)HOLY WAR!
Microsoft has nuked us...anyone up for the fight?