I think I've got a fix in to allow 280 character tweets to go through reliably BUT Mastodon and twitter don't count characters the same way. No matter how many codepoints are in an emoji Mastodon counts it as 1 character so 💩 and 👩‍👩‍👧‍👧 are 1 but twitter counts those as 2 and 11 characters respectively so Tweet splitting/truncating will still happen if people use emoji and go over 280 chars. There's nothing I can do about it sadly.