"But they still understand me," is not an excuse. The person on the receiving end of an email or post forms an opinion of the person whose writing he or she is reading (for instance, most people think I'm a pompous ass), and that influences the gist of the message being conveyed. In other words, "they may not understand you" in the manner you believe to be the case.
I've noticed that too. Not that you're an ass but that intent and positions can be twisted or misunderstood. Sometimes it's intentional but mostly because the poster wasn't clear or complete. Then there is the very useful /sarcasm.