Okay, actually it's just something that occured to me when I had nothing else to think aobut...
First, we need to agree that most HD riders use a low hand with two fingers extended as a greeting. A few use just the index finger. If it's the middle finger, that's a whole other topic.

Now, even most HD riders don't know how this got started, but I have a theory:
Most use the two fingers, 'cause they're proud to be on a
V-twin.
The one finger wave? They're 1%er's. They're rebels, and want you to know not to mess with 'em.

Or they're idiots who didn't get the memo.

Hey, I didn't say it was a good theory!
So, I now propose the Honda salute. Four fingers, instead of just a measley two.
Now, let's let the HD forums start a topic "Why do Honda riders use four fingers to wave at us?!?"
(see what happens when I have too much free time?)