I initiate a salute for two reasons:
1. If I die and my opponent did something I consider exceptional, well skilled or kewl and out of the ordinary,
2. I die or win, and wish to simply say hello or acknowledge a pilot I know and respect.
I will not return a salute if:
If I died and I don't really know the other pilot, and I didn't do anything exceptional (except die gloriously), or otherwise don't know any reason I should get a salute. I figure in that case it's just gloating on his part.
Otherwise, salutes should be return if only to acknowledge another cartoon plane aficianado.