Wrong again. If you want to make it right there are all sorts of assumptions you can make. In this example, a period is the right punctuation. Next would be a conjunction. A semicolon, while not completely perfect would be better than a comma, since the use of a comma, by definition, makes the above a run-on. No English teacher I ever had taught anyone I ever knew to do anything other than get it right until such time as you are a published writer, at which time you can do pretty much anything you'd like.

Moving the expressions from back to front or front to back is how we teach third graders to 'see' the two, independent clauses and not where to put a comma, since a comma alone here isn't sufficient. There is no 'interjection' or 'weak exclamation' here.

Hurry! We need to get there now!

Hurry, we need to get there now.

That's what you are trying to twist this to in order to make your point. You can't just break the rules when you want to. If you tried to teach that crap to my daughter me and you would have a come-to-Jesus of a parent teacher conference.