Stumpy-Fingered Old Man Scribbles In Diary

We've all been looking at this Twitter thing wrong, at least as it relates to Donald Trump.
Suuuuure, he's doing it in a totally inappropriate way, and suuuuuure, it's unbecoming of a President to call out everything from businesses to federal court judges using the service when you're an elected official, but what if Trump doesn't know Twitter is public?
Like, what if this poor old guy thinks it's a personal diary or something?
Related: Dear Diary, Press Conferences Are Terrible...
No, seriousl