At IndieWebCamp 2012 a bunch of participants noted that there are several building blocks we need in order to advance the indieweb beyond just being a collection of hyperlinked independent websites. One of those is the notion of Indie autosuggest, in particular, for typing/picking a person, e.g. using their name or alias (@-name or otherwise).
There are plenty of documented design patterns around the web for single line, static-content inputs (e.g. tag inputs, email To/CC/BCC), but hardly anything for multi-line, dynamic-content UIs where autosuggest is context-sensitive.
Examples in the Wild
In conclusion, there is almost no consistency between UIs across platforms or even between platforms.
Common denominators (add more as they emerge):
The 2012 Portland Sign In With Your Name and Open Real Time Search Engine sessions both discussed indie autosuggest a lot, and resulted in some code demonstrated as part of the Open Follow hack (code on github).