Quote Originally Posted by RSP View Post
Booming Blade doesn’t create a cone or line effect, though.
No, its a kind of a sphere but only affects one target - its 'Self (5ft radius)', so again, not 'Self'.

Also, lets be honest here and realise that the change from '5ft range' was awful and makes no sense - it seems purely to try to ban it from Twinned Spell, but they didn't want to make it a 'Self' spell that cost a bonus action like the Smite line of spells because the effect of the spell already acts as a weak Extra Attack scaling intended for casters not martials who could also Extra Attack with their Action.