It's definitely not intentional. It's just pattern recognition trying to recreate a humans voice and facial expressions from an extremely limited set of information. The less information, the more extrapolation has to take place, and if you provide basically no information but with a specific emotional signifier on it then that signifier becomes the main information converted in the text. Had you typed a sentence or two of your other comment with the 2 dots on the end people probably would have read it more charitably. But as it stands, the 2 dots are the only information available and so it reads like sarcasm and dismissal are the singular goal of your comment. This interpretation can be prevented by providing more guiding information in the comment.