I am not aware of any system requirement. For me, it just works.
I have tried this on IE, Firefox and Chrome, it works on all of them.
After typing this much, I saw a flash of light and below might be the reason why it "just works" for me.
I use a screenshot taking tool, which allows the captured image in clipboard to be in png format.
PNG is my favorite, and most suited for taking screenshot of computer applications.
Another advantage is that PNG content can be 20 times smaller than BMP.
So, my clipboard image is very small sized because of:
- PNG format
- Small resolution because I capture region. Say, all my images are smaller than 600x400 pixels.
I use Greenshot because it is awesome and free/open source.
My workplace does have option of SnagIt, but I won't use that heavy/expensive/closedsource application.
Prior to that I had used a freeware named Gadwin PrintScreen. Both softwares had PNG option.
Imagine a normal full-sized printscreen having 2MB BMP data in clipboard.
SCN requirement for Inserting Image is:
Maximum file size: 1.0 MB. Also, please note that images larger than 640px wide or 400px tall will be scaled to fit those limits in your content.
Here I am pasting a small BMP created using Paint application of Windows 7.
Let's see what happens.
EDIT: BMP pasting worked for small image, and Jive is smart enough to store it as PNG 
In order to test my theory, please try out a screenshot tool with png option or in-built snipping tool of Windows 7 for a smaller image.
At the very least, you could open calculator application, and do Alt+Printscreen (captures active window, not the entire screen) so that a small image resides in clipboard.
Then try pasting on SCN and pray.
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