Don’t warn me Mr. Uploader, I’m not the one that’s making it not square!
In light of the change to circle avatars, maybe that warning should say that the aspect ratio is not 1:1 or something more appropriate. Telling us our avatar isn't square when Discourse is also displaying it cropped into a circle makes the warning confusing, especially if your image was just 256x257 or something and you didn't realize it's not a perfect square.
<blah blah blah blah