I'm tempted to add the :3 tag, but neither example has eyes showing...

I don't think that's important. The tag is all about the mouth.

Shou said:
Heya, Nazrin, how ya doin'?"

And now I can't help but see Shou as Joey from Friends.
I'm not sure if that's a good thing or not.

I think 星君 might be a reference to one episode of "Chargeman! Ken" which more or less became a meme on NicoNico Douga. If that's the case then the pronunciation would be "Hoshi-kun", and it is also the name of a character also refereed to as "The Mysterious Handsome Boy" (which might explain the usage of it here?). And as with most things viral on Nico Nico, it's been crossed with Touhou in many different ways...

I've seen it used as a way of referring to Shou, but only really on NicoNico, but I'm not sure if this is where the nickname first originated.

Most straightforward example;
http://www.nicovideo.jp/watch/sm10751751
http://www.youtube.com/watch?v=3i3HOVnIRfM

whatdoyouwant said:
I think 星君 might be a reference to one episode of "Chargeman! Ken" which more or less became a meme on NicoNico Douga.

That's possible. Hmm...no source for the image, so I can't check Pixiv tags, blog comments or whatever to confirm

To make a touhou comic, you need a pun and an explosion!

JesusK said:
To make a touhou comic, you need a pun and an explosion!

The wise teachings of Bomber Grape.