Sometimes to minimise the post work I put the proper sky background in the scene as a CoronaLightMtl
I see now that the CoronaSun position does not reflect the physical position of the sun but rather serves to define the light direction (yes, that's the reality)
So, to get the sun visibility together with the Bloom and Glare effect I have to make the background transparent a little bit or to put the Corona Sphere light in front of the background
Just wondering if there are more options )