Users can select a display name that’s different from their actual username for example “Arthur Besse” is [at]cypherpunks

Additionally since they are not a native pearthchat use you would need to add Lemmy(.ml) to tag the instance of that user.

So @cypherpunks@lemmy.ml should be the format.

Edit:hmm, wonder if its because I’m on lemmur. Try https://lemmy.ml/u/cypherpunks