@jkb I actually don't agree with this purely for the reason that making Mastodon seem like a viable Twitter replacement without asking users to also drop all of their tweets, content, followers, etc makes Mastodon more likely to succeed as a mainstream project rather than a relatively fringe one.
@aredherring Posting the same content on multiple places is fine, it's automatic mirroring that irks me because it has basically no value unless you follow the link and go to Twitter
I use a auto-mirror service (crossposter.masto.donte.com.br), and the posts are generally full of the same content I'd post on twitter.
AFAIK the only time there's a link to twitter is if the twitter post has a link to a twitter url (Including quote-replies) or plain retweets (which include the content, as well as the URL for the retweeted source).
@atrus Manual cross-posting means you select the content you want to share elsewhere, and you may add a bit of effort on top of that (captioning pictures or adding content warnings). Automatic mirroring is indiscriminate and will happily copy everything regardless of relevance.
My complaint was triggered by a toot that was a simple "RT some @ Twitter", including a single image, uncaptioned, uncommented, vague in context, with a broken link as the original tweet was deleted in the meantime.
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