Where wild minds come to rest
Hmmm, I don't do either of those things.
Definitely zoning out to music and I guess what others would see as talking to myself or making gestures.
In general I agree with these ideas you listed instead of the zoning out to music that other's gave; mainly because I never use music to zone out for myself for MD. Also in my city, many people would listen to music/radio while doing exercise, and you can't tell if they are not listening to you solely because of focusing on their radio or zoning out like you guys.
However, I think a symptom "dead giveaway" may only be dead giveaway for us MDers;like Theaxe first case to a young man, only after she figures out what MD is she can catch what the young man is truly explaining. For others, they simply don't understand. Not able to focus on something or zoning out, a general thing that causes us to get into trouble, may easily be regarded as ADHD or even just laziness. Or in some cases, if the MDer encounters more difficulties in life, it can easily be turned into depression, leading his/her case to be covered up and the symptoms never be discovered. Therefore, IMO, the sad truth is that there is no "dead giveaway" symptoms for MD, until the day MD is more well-known to the public that they start to get the concepts and differences of us and other people suffering mental problems.
My MD is immensely private. I make sure I am not seen when I am rolling around in my bed as I listen to music. Listening to loud music on my headphones is equivalent to cooking up the crack, and then lying down to shut my eyes and daydream is the equivalent to smoking the crack.
But in answer to your question, because I keep thinking I'd never know if someone had MD because I associate it with being very private and trying not to get caught, I assume most others are doing the same, so how would I really know? Instead I look for key talking-points. I met a young man at work years ago who told me of his vivid imagination and wanting to write a book about his paracosm. I had just figured out what MD was, and asked him point blank if he fantasizes about this world more than normal. I had to reveal that I had MD in order for him to trust to tell me, and when I explained what it was, he admitted he did the same thing.
The reason I could identify is because he was young and eager to express this creative world he thought of. I did the same as a teenager. I used to tell a few friends about movie plots I could come up with, and what actors would be great to star in my movie. He was also quick to change moods, and was unusually sensitive. I too, am over-sensitive. He was also extremely bright, but a little fuzzy on focusing. All things I knew I was like as a teenager with MD.
Another young man I used to know on a multiplayer video game had funny symptoms that back then I didn't know was MD yet. We used a live-chat program to speak on headsets and he used to say these clever things, and under his breath repeat it or elaborate not really cluing in that I could hear him do this. Then if someone said something clever to him, he did the same thing, he'd laugh out loud then whisper the remark under his breath. No one called him on it. It was a little weird thing to do. But I recognize now that he likely absorbed the comments, and repeated them because they instantly went into his head as a sort of daydream-check-out. If he liked the comments, he whispered them to himself. If they weren't worth it to him, he didn't do this. This was about ten years ago, and I didn't know what MD was yet, so I couldn't confront him with it.
Now that I know what MD is, I just check to see abnormal public behaviour that the person might be trying to cover up, or is embarrassed about getting caught. So the low whispering to themselves (again, it has to be specific because I know almost everyone 'talks' to themselves), funny movements that don't have to do with anything actually going on around them, and whether or not some of it happens with headphones on. I sometimes look over at people driving at red lights to see if they're in a zone. I know what it might look like as someone having MD, so I just try and figure out if the 'zoning' looks like they're just grooving on music, or if it happens to be a bit more with changing facial expressions, etc.