Upvoted, because I would read that "things you can't do on the subway" article.
- Mention aloud that you see a rat
- Stare at or talk with the homeless guy/conspiracy theorist
- Make eye contact with other passengers for more than 500ms
- Hold or read something that has Arabic lettering on it
- Urinate
- Smile
Of course, it's always easier to twist and contort statements involving racial stereotypes to paint the person posting them as a racist, than try to actually get the joke, so I expected that to happen.