https://www.politico.com/story/2019/05/16/trump-scavino-1327921
(interesting excerpt from this article)
While Trump used to dictate many of his tweets to Scavino, who would post them on his behalf, the president has grown more accustomed to tweeting unilaterally from his own account. When he does dictate his tweets to Scavino, the president is particular about exactly how they should be written, specifying capitalization and punctuation, White House officials said. The result is a sometimes-confounding presidential style guide in which the first letter of words like “collusion” and “witch hunt” are almost always capitalized.
The White House has created a separate review process for tweets that don’t originate from Trump or Scavino. Staffers propose a tweet, circulate it for feedback and then send it to Scavino, who sometimes “Trumps it up” before getting the president’s approval, according to a former White House official. Scavino has spent so much time around the president that he is an expert mimic of Trump’s speech patterns and predilections.