Bluesky replies carry parent/root references, so the author is notified
without a mention in the text. The prefilled "@handle" only created a
redundant mention facet, and used the reposter's handle for reposts.
Direct messages are plain text sent to a conversation, so the prefill was
useless there too.
In Mastodon's send_message, the author check compared the bare acct with
a list of "@acct " strings, so it never matched and duplicated the mention.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
