Okay, so this isn’t a very pretty photo, but I chose it on purpose because it’s super noisy, and any new compression artifacts would show up right away.
In #1, I used our image uploader, which reduced the size by 50% (even though my file was well under the 2MB limit), and introduced a LOT of noise.
Specifically, the image was at 2566×1494, and was uploaded as 1024×576. That’s gruesome, but the compression is even worse than the rescaling. That’s an ugly, ugly upload.
In #2, I uploaded the photo to imgur, right-clicked to copy it, then pasted it directly into the post. BOOM! Full size, baby.
The disadvantage is that the pasted image doesn’t open into our lovely full-screen image viewer….but the fact that our full-screen image viewer is blowing back up an image that has been reduced by 50% in size and compressed using who knows what makes that feature not exactly useful either.
However, right-clicking on the larger image and selecting “Open in New Window” works dandy, and looks pretty darn good.
I’m still working through this, and invite other folks to upload and test this too! And hey, now that I’ve figured out that copy-paste works for pasting full-size images, I may actually upload a photo that I like, instead of one that I chose specifically because it was already pretty bad. 
And I do highly, highly recommend getting a free imgur account. I use it all the time for copy-paste processes like this, and other stuff too. It’s fast, easy, and non-invasive. You’ll dig it.