"_If you touch the👇black point then your whatsapp will hang_", says the message that's being sent around, and it's right. It's a text rendering bug, the same as many others -- which isn't interesting. But the characters it's using, Unicode RTL and LTR marks, are worth knowing about.

Thanks to everyone who suggested this subject!

The Unicode Bidirectional Algorithm: http://unicode.org/reports/tr9/

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