This will be an ongoing topic I continue to add to. You can read part one here. I am also covering it on Instagram - you can see the original post here.
Some of the key differences between how ADHD and autism are characterised in conversation is that people with ADHD can experience more impulsivity and distractibility, while people with autism may feel more comfortable when the conditions and expectations of a conversation are clarified in advance.
ADHD: Missing social signals due to inattention
ASD: Difficulty "intuitively" picking up on social cues
ADHD: Distractible and difficulties sustaining focus in conversations
ASD: Difficulties understanding subtext and body language in conversations
ADHD: Need for stimulation to feel engaged
ASD: Difficulties in multitasking (in social communication)
ADHD: Impulsive behaviours
ASD: Planned social scripts
ADHD: Tendency to go on tangents
ASD: Tendency to talk only about their special interests