Choose the caption bubble to begin. If you want to upload a custom bubble or alternative image then submit the caption first, then edit the comment and attach a "Place img". Once the image is approved you can use it by editing the caption again.
Tested that style on a LAN a few years ago. Really tiresome on my lower arm muscles since I'm not used to it. But that style vs. normal style matters as much as invert mouse or not ;)
fazz
