Your mix tape isn't fire, it's smouldering at best

I always assume people doing this are unhinged/crazy and I definitely don't want to deal with that.

Sometimes they look nice enough.

Usually what happens is myself and everyone else on the train look at each other, have a shared look of "Morons? Am I right?" and then when that person leaves, we all share a group laugh.

So I guess what I'd say is, if you do this, know that everyone is laughing at you. If you say you don't care, that's a lie, you do care, that's why you're doing what you're doing. This is not positive attention, this is negative attention. Please take a moment and reflect to be a force for positivity and not negativity.

The new trend I’ve noticed, actually is people SINGING/RAPPING along to the music on their headphones, like, fully as if they were the only ones there, while on a packed train.

I mean, i guess it’s better because it’s not as loud as their shitty Bluetooth speaker at max volume peaking like crazy, but it is super weird and very fuckin annoying.

Like, cool, we get it you’re so super confident and think youre as cool as the person you’re listening to in one of their music videos. But you’re not. Because you sound like shit and you’re a dick. Everyone else is getting through this train ride, why the fuck do you think we want to hear YOUR rendition of what you’re listening to? Like, I really can’t decide which is worse. One is way louder but one is way fuckin weirder. People who do either of these are true assholes.
Genuinely not necessarily true. I used to do this when I was younger. It wasn't because I wanted attention, I just like the feeling of being surrounded by music
- Genuinely, the world does not want to always take part in what you want. There are rules to society that most of us at least try to follow out of respect. Time and place to be surrounded by music. I’d definitely say on the bus or train is not the time or place. Agree?
- I masturbate on trains—not because I want attention, I just like the feeling of cumming and I wanted to cum.
- headphones are both more polite and more immersive thwn carrying around a speaker to annoy others
- when I was younger.
  
  Looks like you’re still not forgiven :)
- You're a bad person.
Some guy got stabbed on the subway in Toronto a few months back because he asked a guy playing music to turn it off. It really is a crazy world out there.

Nope, not worth it. I've stopped trying to convince others to be considerate in public. They'll either ignore you or blow up and get aggressive. I'd rather just try to ignore them myself and move on with my life.

And at the end of the day, I'm also not some authority figure like their mom or dad; I'm nobody to them. As much as I may not always like it, strangers don't owe me anything, including their consideration.

Strangers who use public spaces absolutely owe other people their consideration. It's part of the price of admission to a public space. It's not enforceable in practice but I'd be surprised if a certain level of being inconsiderate is even legal in most public spaces.
- I don't disagree with that in theory, but like you pointed out... Who's going to enforce it in practice? Shouldn't have to be me, or anyone else who doesn't work for public transit.
  
  Obviously there's a point where I'd say something if a person was being truly inappropriate, but I'm not risking my neck over music on a bus.
If people cared about your opinion on their intrusive actions, they wouldn’t be doing anything intrusive in the first place.
The real caption should be "Am I the only one who makes memes about my tough guy delusions?"

Maybe OP found the one truly ignorant but considerate person in the world who has done this. Everyone else knows it's a waste of time.
I have shaped my life to minimize exposure to anyone else and the first half of this is a good summary of why.
This is the most reasonable take here.

I've tried this. Guy next to me was playing a video game on full blast that I can hear over my noise cancelling headphones. I asked him if he could turn the sound down.

He said "F you! This is my console. I do what I want! You're the only one complaining so shut the f up".....

"Wanna hold a referendum on that?"
IMHO you would have been within your rights to yank that guy's console out of his hands and smash it.

Of course the risk escalating wouldn't be worth it, but you'd have the moral high ground at least.
- Someone being obnoxious does not give you the right to damage their property.
  
  This is an absurd and extremely juvenile take.
- In many places, what you suggest would be charged as an assault, and destruction of property.

Start up your Bluetooth speaker. (Buy one if you haven't got one. It doesn't have to be good, just loud.)
Ramp it up to 11.
Start the most annoying obnoxious sound you have, (that you have already downloaded).
Stand next to the person playing the shitty music and aim the speaker at then.
When they complain about your annoying noise you reply, "You started it."

Is this the real reason polka was invented?
- Hey! I'll have you know that the "Polka King of the Midwest" doesn't take kindly to comments like that!
Yoko Ono it is!
- Now now, there's no need to be so evil!!

uses colorful metaphor
- Well double dumbass on you!

Yeah I don't need the tweaky dude stabbing me on the train because I didn't like his music, but thanks

i wonder what would happen if you just start acting really into it and singing along terribly with enthusiasm.

I'm American, I'm not trying to get shot

German here. A woman was starting to play loud music on her phone while I was sitting at a bakery having a cup of coffee, trying to relax from a bad morning. I opened Spotify, checked for this song: https://www.youtube.com/watch?v=PDBDtIOxUsI Every Maaaaaamaaaa I was singing loudly along. She lasted half of the song then fled the scene, even left her coffee on the table. My ears were bleeding, but it was worth it.

Fight them with the most terrible old people song you know in your country, be aware that it might hurt you too.

No all hero's wear capes....it'd be cooler if you did though
Or you can choose a mixture of terrible and majestic and sing with all your might.

https://www.youtube.com/watch?v=0q6yphdZhUA
- Here is an alternative Piped link(s):
  
  https://www.piped.video/watch?v=0q6yphdZhUA
  
  Piped is a privacy-respecting open-source alternative frontend to YouTube.
  
  I'm open-source; check me out at GitHub.
Here is an alternative Piped link(s):

https://www.piped.video/watch?v=PDBDtIOxUsI

Piped is a privacy-respecting open-source alternative frontend to YouTube.

I'm open-source; check me out at GitHub.

Yes. We shoot people for accelerating from a stoplight too fast here.

Try that in a big town

Yeah I mean I'm not much of a fighter and I've gotten put in the hospital for something similar, so now I avoid confrontation like the plague.

I envy your bravery

In Australia these people are deros huffing glue or drinking bowlers run red wine from the bottle. No thanks, I'd rather avoid them.

Do people unironically refer to playlists as mixtapes?

Why not? They fill the same niche functionally.
- I just think it's odd that such a long-outdated term is still in use. Something about it being more specific than "tape" makes it more weird to me.
Some people are just old enough to remember using mix tapes.

I'm too puss. Especially if they look even remotely like they could put up a fight. I just sit angrily the whole time.

Did it at the gym once, was watching a show while doing cardio with my headphones and could hear another guy's music over it. I just yelled without stopping what I was doing "Hey bud, no one wants to listen to your music, use headphones!" and the guy could see everyone's smirk, he got the message.