The one useful thing I was ever taught in HCI was always give advanced users "hidden" short cuts and features.
Things a noob is not interested in but a power user can easily take advantage of.
@rjstelling - Auto linking @username to users profile (a la Twitter). It's already the de facto standard in comments.
[#102] - Simple question linking, this would expand to the title linked to the question, i.e. Additional Badge Ideas
[#102#160] - Simple answer linking, as above the the second number specifies the answer i.e.: Additional Badge Idea
Are these useful?
Edit: The @username idea has been implemented.