Note how the bloom in the second screenshot is completely faked and baked into sprites, not created in the framebuffer:
That's a good eye you have there, thank you.
I'm still at a loss as to the best way to draw the original sprites before bloom processing, etc. My guess would be that simple shapes of 3-4 pixels in thickness would do it? The post processing should then eliminate aliasing and make the pixels more vector beam like?