If you can find a convenient reason to email an adcom, I think it can be handled therein.
For example, after I got my interview invite (it was with an alumnus who had related experience in my post-MBA aspirations) I emailed the adcoms to thank them for going the extra mile to match me with someone who was on a similar career path.
Maybe the match happened by coincidence, but I gave them the benefit of the doubt. It was a great opening to lead into "how much you appreciate the school's attentiveness to your career goals", "how much it strengthens your opinion of the school" etc. Personally, I didn't take such an explicit route; I attempted to communicate my regard for the school by keeping it as a simple thank-you note... hopefully that message wasn't lost in the subtlety. I did receive an email back from adcom thanking me for the kind email.
Anyway, if you are going to email adcom, I say do so but add something else in there that will be worthwhile to them. Perhaps provide some positive feedback on a recent info session you attended, or how valuable their employment placement guide was when it came down to deciding which school would be your first choice. And I guess this is obvious but I'll say it anyway: don't attempt it unless you actually mean it! I'm betting they have finely tuned BS detectors.