Whenever a light source is directly seen in a reflection, it gets rendered as a bright white orb. This happens with both Point and Spot and Area lamps, sun lights seem to be the only ones not affected. Is there no way to get rid of this render breaking artifact? I'm assuming this must be a known bug with Eevee / Screen Space Reflection as it's been around for many Blender versions.
$\begingroup$ Just realized after posting this: What's most likely happening is that the orb is the specular reflection of the light, which naturally appears sharp in mirrors that have no roughness. On a normal rough surface you definitely want this... in a mirror reflection however it looks like a floating disc of light, so I'm probably looking for a way to disable this precise specular reflection on the mirror surface only. $\endgroup$– MirceaKitsuneMay 9, 2021 at 16:16
$\begingroup$ I can confirm this theory: If I set the specular value of the light to 0 the issue goes away. It's not a viable solution as I still want specularity on other surfaces though. I need to turn it off on just the mirror, which I tried but couldn't find any way: GlossyBDSF has no option for such, PrincipledBDSF does but setting its specularity to 0 doesn't solve this oddly enough... couldn't find other material settings either. $\endgroup$– MirceaKitsuneMay 9, 2021 at 16:54
I solved the issue and am happy with the results, even if this is technically working around it. The core problem was that I was using a huge light radius: You want the sphere of the point light to encompass and represent only the bulb. I set it to 0.01 instead of the default 0.25: This not only results in the correct shadow softness, but the white orb is now just a tiny speck, precisely how a bright bulb should appear in a reflection! It's also hidden behind a lamp cover so it shines even this way only when seen from the right angle.