American English 101
It's true! Isn't it? (These are two sentences, one an exclamation, the second, an interrogative - even if the interrogative questions the exclamation.)
But what if you wish it all to be included in one sentence?
It's true, isn't it‽ (<---- This mark, known as an interrobang, and doesn't exist on many keyboards, combines both exclamation point and question mark. If you cannot reproduce it by keyboard, simply email yourself with this punctuation copied and pasted into the email. Then (like me), you may copy and paste it at will, even if only as a conversation starter or trivia teaser.
While I'm not a fan of it (I used ?!? in many writings), between 1965-1970 this came into being. It is strictly descriptive and by choice of the writer.