days since someone got bit by “fedi doesn’t let you mention a username in a DM without also adding that person to the DM”: zero
@gardevoir fedi does in general, just the popular apps don't
-F
@Felthry I stand corrected!
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@gardevoir the activitypub protocol has separate addressee and body fields, so you can in theory say "send this to X Y and Z" and then not mention X, Y, or Z anywhere in the body of the post, and any standard-compliant AP implementation will handle it properly (X, Y, and Z will get the post in their notifications)
For some reason (maybe to be like twitter, i assume?) mastodon doesn't do this, instead just finding anyone mentioned in the body and copying that to the addressee field
-F/R
@gardevoir afawk pleroma and misskey also do that, but we're not as sure about that because we've never used either
-F