File this is the "woah" department. So many questions. Why so many tweets with a character length of 23 for unverified users? Why do verified users have such a large percentage of tweets with 135 characters?
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That's weird. Maybe twitter client name can give some clues? Although all software should be updated by now. Another option could be that these are copies (or RTs) of the same message. Looking at the text should give the definite answer.