I've observed that human people communicating through low-bandwidth channels like the one we're using find ways to add nonverbal information to supplement the words. What else is a ":-)" but a nonverbal communication mapped to an icon? Even deeper, people give clues about their state of mind and their feelings when they write. Human communication, even just writing, isn't restricted to statements of concrete facts...and I feel pretty good about that...;-O

To wrap it in a little engineering jargon, when confronted with a bandwidth bottleneck, compress the data. Humans take the wideband channels of verbal + nonverbal communication and compress it down to be expressible in words alone. The "tokens" in the "datastream" you transmitted: "The way our face moves, our eyes shine, our voice shows tones...." each stand for a packet of nonverbal information. You could describe (or transcribe) all the nonverbal messages you're giving off when you're writing a post, and I'd be able to reassemble them into something like the experience of being there.

Less perfectly than really being there; that's what makes it lossy compression like JPEG instead of lossless like TIFF/GIF. But there are ways to get the message across.

A related issue is whether we'd be able to recognize alien emotions even if we knew the nonverbal language. I think we'd recognize most of them, because emotions didn't arise for no reason--emotions like fear or agression, and curiosity in social species like primates, have survival value as a spur to action like fight or flight, or go check out the possible new food source (for the curious types). If evolution converges on intelligence as a good answer in many environments, including those extraterrestrial, then evolution is likely to also equip those intelligences with a set of similar basic emotions.

Higher emotions, though, the ones we developed since we became civiliized, may be hard to convey. Romantic love is a relatively new innovation, arising within recorded history. Could we explain love to an alien?

Captain Kirk must've had faith it was possible, eh?