D&D 5E Light VS Dancing Lights

[DND_Reborn]

Well, there's a pretty reasonable interpretation of Devil's Sight only working in darkness

And there is a reasonable interpretation for why Shadow Blade grants advantage in dim light when a light source (whatever it is) sheds a weak light.

From a design perspective, I actually like the fact that Devil's Sight isn't just a magic "you can see 120 ft no matter what the lighting conditions are" ability.

Some people like it, some people don't. If you look at devils, they all have darkvision as well. So, for them dim light also is considered bright light. Thus the combination of the two (which all devils have) allows them to "see 120 ft no matter what the lighting conditions are". Because of that, a lot of players feel Devil's Sight (the invocation) should work the same way, but RAW it doesn't give you "the ability to see like a devil after all."

As for JC's comment about "dousing that candle", it actually seems to imply the power can't function you are in bright light. Not a very good comment IMO although I get the "flavor" he is trying to add.

 

[Asgorath]

And there is a reasonable interpretation for why Shadow Blade grants advantage in dim light when a light source (whatever it is) sheds a weak light.

Right, we can just agree to disagree here. Shadow Blade has "shadow" right there in the name, and a dim light source like Dancing Lights doesn't magically create shadows in an area that is already brightly lit. If you're standing in the middle of an open field in full daylight, Dancing Lights isn't going to suddenly create shadows that allows your blade literally made from shadows to work better IMO. But, if you've convinced your DM to let you use it like that, more power to you (or as JC would put it, "follow your bliss").