Each group of characters beginning with a backslash and followed by three numbers is an "Escape Sequence". Each of them represents a single character. These are usually used for characters that don't exist on your keyboard such as non-English-language characters and symbols.
My guess is that when counting the characters, Twitter is counting each of these groups as a single character but when displaying them to the browser it is printing them as four.
Some of the escape sequences available are "control characters". These tell the computer to do something such as playing an alert sound or moving the cursor left or right or up or down or deleting the character to the left of the cursor. Although none of them are the last one I mentioned (deleting the previous character), he might have used that character to confuse Twitter as well.
Interestingly, when turned back into normal characters, it is quite repetative and looks something like this:
í µ í ³ í µ í ³ › í µ í ³ œ í µ í ³ í µ í ³ £ í µ í ³ ¨ í µ í ³ í µ í ³ › í µ í ³ œ í µ í ³ í µ í ³ £ í µ í ³ ¨
The explanation he gave was "Пишите в DM, всегда на связи )" which Google Translate tells me is "Write to the DM, always on connection)". I'm not sure exactly what that means or how it helps.