Pasting a mixture of unicode glyphs including squares like 🟩 (U+1F7E9 / :green_square:) into a chat when using the client in Windows will:

• Render acceptably (though in black and white) while pasted into the message editor
• For an extremely brief window (<0.5s), render correctly in the chat window

🟩⬛🟨⬛🟩

🟩🟩⬛⬛🟩

🟩🟩🟩⬛🟩

🟩🟩🟩🟩🟩

• Suddenly revert to a broken representation where only the black-and-white glyphs render

:large_green_square:⬛:large_yellow_square:⬛:large_green_square: :large_green_square::large_green_square:⬛⬛:large_green_square: :large_green_square::large_green_square::large_green_square:⬛:large_green_square: :large_green_square::large_green_square::large_green_square::large_green_square::large_green_square:

It feels like Slack is adjusting the message after I post it, though I guess it could be Ripcord or Qt.

If I copy the message using the right-click menu in Ripcord, I see:

:large_green_square::black_large_square::large_yellow_square::black_large_square::large_green_square: :large_green_square::large_green_square::black_large_square::black_large_square::large_green_square: :large_green_square::large_green_square::large_green_square::black_large_square::large_green_square: :large_green_square::large_green_square::large_green_square::large_green_square::large_green_square:

This kind of message has become popular with Wordle (and a growing number of derivatives), but this rendering makes it really hard to read.

I've tried using unicode-friendly fonts, and switching font rendering engines, but nothing seems to render the message once it's been processed by Slack.