Heh. That's one, among many myriad reasons, why I got out of teaching before I really started. Couldn't care less whether it was proper, so long as it worked, but realized that grading student papers I wasn't likely to see much of either. (And no, the problems aren't exclusive to freshmen. You can find truly atrocious prose- even worse than mine!- in graduate papers.) Working for decades with folks who were going to obsess over proper usage was also rather unappealing.
That said, I've stopped the practice for the most part, except perhaps at the very beginning of a post or essay. If the continuation is that big a deal, why not either start a new paragraph, or use a dash? At least that's what flashes through my mind while editing . . .
Ex ignorantia ad sapientiam; e luce ad tenebras