I used workaround you suggest, works fine for me.
Also i’ve pulled out format string from original TwitterKit bundle and now sharing looks exactly as it supposed to be in case if current issue would be fixed 
//Subject
let subject = String(format: NSLocalizedString("tw__share_tweet_subject_format", bundle: frameworkBundle, comment: ""), tweet.author.name, tweet.author.screenName)
//Body text
let text = String(format: NSLocalizedString("tw__share_tweet_generic_template_format", bundle: frameworkBundle, comment: ""), tweet.author.screenName, tweet.permalink)