But I agree your latest one doesn't seem to jive with the reference.
I never understood that line either. Let's see if we can figure it out! To the blame-mobile 
That... doesn't address the particular line in question, but seems particularly relevant to your latest post!
Comment about which unsizing coercions are actually performed is still relevant, but this is generally an improvement. I'm happy to have this merged with an issue created (either here or on the main repo) if we can't reach a decision now.
It never got filed but should be.
I didn't see any discussion or explanation about that line though.
...plays a bunch....
Fully qualified syntax doesn't actually disable auto-deref of function args as far as I can tell. That includes for the receiver of methods. It doesn't do auto-ref or array unsizing like method call resolution does. Maybe it just makes the receiver act like any other parameter?
Definitely you can do other coercions on receiver, like &mut T to &T, with or without fully qualified syntax.
Yeah, I still can't make any sense of that particular line. And I think exactly what fully-qualified syntax changes should be made more clear too. The current wording around "avoiding deref" is misleading IMO.