Here are a couple of user scripts I use to make things a little easier for myself on Danbooru.
They should work in Opera, Chrome, and Firefox with Greasemonkey
This script lets me bring up the note history when viewing a post by pressing Shift+Ctrl+S.
The history features an optional diff view with additions underlined and deletions striked out, to easily spot the changed parts of a note.
It also shows changes to the size and position of a note. By clicking on a history entry, you can view the position the note has or had in the image.
This script lets me create notes with a keyboard shortcut and position them via the mouse.
To use, position the mouse pointer where the note should start, press Shift+Ctrl+D, then move to where the note should end and either press Shift+Ctrl+D again, or left click. When editing note text, Shift+Ctrl+D will save the note.
Another, more full-featured alternative is Glasnost's translation helper script.