Re: Two different people
Its difficult to convey facial expressions in a written piece (email, IM etc), which along with body language tells the listener what the intent is. Lately I have seen some work-related emails going back and forth where people are actually putting :-) and other emoticons. On first look, it appears quite odd in an otherwise serious work-related email.
The converse is probably a better option, which is, be polite in your written words so others don't get the wrong impression.