Heh, hostility is fun, right? I am not a C programmer, please pay attention. I have used colorkey, but that is not a straightforward way to increase speed. Since it involves a check on each pixel, some images may not benefit (and in fact will lower performance) if there isn't much transparency. Wheras a 'blit' on matched pixel format surfaces can be a simple memory copy operation, depending on the platform.
To illustrate a use case for an "unsafe blit": In tile map drawing, you will be doing potentially hundreds of blit operations. Since tile placement is very straightforward, you can be sure there will be no out-of-bounds blitting. You can enforce pixel formats when the surfaces are loaded. So, format checks are only needed when surfaces are loaded, not every time there is a blit operation. (Also, this is just one potential scenario, please don't elaborate on different way to render a tile-based map, just stick to the topic: "unsafe/fast blit")
As is, the 'blit' operation removes several chances for error, especially for people who don't care to convert surfaces or set clipping regions, but it does so at a performance cost.
It could be as simple as making the following function available to pygame, perhaps in some inconspicuous place, not a part of the surface class...in order to discourage abuse:Â