Seems like they are real.

They're not Tongue

It's something Blockchair made up:

Q&A

Quote from: MrFreeDragon on August 17, 2020, 05:56:46 PM

Can you please clarify, what is the type of these d- and s- addresses?

This is how Blockchair.com shows OP_RETURN. From the main page the search field doesn't show them, but you can replace a Bitcoin address in the URL to find them: https://blockchair.com/bitcoin/address/d-d0d953f2e7043342540a1407243e49fe.

WOW!

That's wild!

Looks like D is not the same as d and S is not the same as s.

Sorry, my answer above is correct, but not accurate to your point.