Is "Show 'x' color only" on the list? How about a bubble maker to preview text positioning? Associate a second text area anchored to the pushpin but movable so you can preview english text without the kanji and discussion in the main note. Maybe with selectable fonts and font sizes. An option to show note on mouseover? Oh! And add a Thumbtack-tan pushpin!
This is gonna be so awesome for my site! n_n
Have you thought of a name for it? Wakaba Notes, WakaNotes?