This string was found by @w - I have confirmed its presence in the Threads APK from apkcombo, "Threads, an Instagram app_289.0.0.68.109_apkcombo.com.apk", sha256 83a1f270aa2447f4e7310072b4d3217f9af8a03b7679b7760db03ff0bbf8e432, valid signature by "C=US, ST=California, L=Menlo Park, O=Meta Platforms Inc., OU=Meta Mobile, CN=Meta Platforms Inc." (rsa-4096 + sha-256, cert expires in 2053)
at offset 0xB7AE in assets/strings/en_GB.frsc
"Soon, you'll be able to follow and interact with people on other fediverse platforms, such as Mastodon. They can also find people on Threads using full usernames, such as <b>@%1$s</b>."
cc @FediPact