This website used to allow embedding text messages with OP_RETURN, here's an archive from 2015: web.archive.org/web/20150718052659/http://eternitywall.it/
As of January 2024, it seems to read-only mode, where it simply indexes matching transactions that were made via other means: web.archive.org/web/20230929075331/https://eternitywall.it/
There were 3191 hits for the search term:
git grep '\bEW '
in our data starting with tx a3b3af21514bd79a4cbcac9916a8514636a72d813539192214542fd85247082e (2015-06-24):
EW Eternity wall is live
up to the last entry on tx 28820bc14cf2cfda58ecbc9ac6df3f41a1cb90f4246543f01ba42a5e9dac3cf8 (2023-06-15)
EW May our friendship endure, signed by hg, kty, wjj, and xyz.
no doubt initials of 4 Chinesepeople. A blood brother oath comes to mind, akin to the Oath of the Peach Garden. Will these four be the ones to take down the evil dictator Xi Jinping?
The very first message gives away the name of what we assume is a web-based upload system, "EW" being its advertisement signature added to every message.
Running bitcoin-cli:
bitcoin-core.cli getrawtransaction a3b3af21514bd79a4cbcac9916a8514636a72d813539192214542fd85247082e true
shows that the messages are encoded with OP_RETURN:
  "vout": [
    {
      "value": 0.00000000,
      "n": 0,
      "scriptPubKey": {
        "asm": "OP_RETURN 455720457465726e6974792077616c6c206973206c697665