The attached diff does two things:

(1) Add a "ADD_TO_NOSY" configuration option which can 
be used to set a list of users that are automatically 
added to an issue's nosy list upon issue creation.

(2) Updates the logic to be a little more careful.  i forget 
why i ended up needing to update these checks, probably 
as a result of #1.

No idea if you have any interest in this type of patches 
or not as i don't really know where you draw the line 
when it comes to providing some default/basic/useful 
configuration or just letting users do it all.
let me know if you don't as i will probably have more :-)