I'm sure had you omitted it - instead of that reply there would have been a series of comments talking about how Microsoft actually has a track record of doing things like this. It's impossible to please everyone on the internet but I very much appreciate when people lean towards making their communication clearer.
If you can tell sarcasm from text, that doesn't mean everyone can.
For my part, the smiley face was much-appreciated as I've seen people who genuinely would think that with a straight face.
--- EDIT: Spelling of a word