Tweet quotes are no longer supported as we looked at user engagement statistics and in the instances where tweet quotes were used by authors, users were simply not engaging.
Alternatives to Tweet Quotes:
Tweet the quote on your account, then embed your tweet directly into your Bertie story. Readers can then interact directly with it and retweet.
User a service called ClickToTweet. This will generate a link that you can use as a hyperlink in your story. It will even do some level of tracking for you if you desire.