Between WordPress 3.0 and WordPress 3.1, code was added to change certain characters in image captions into their HTML/ASCII character code equivalents. However, some people like to include links in captions, and this new filter broke that ability by swapping valid link code (albeit with strict limitations on the use of single and double quote characters) for HTML characters.
I love the [Post Editor Buttons](http://wordpress.org/extend/plugins/post-editor-buttons/) plugin for WordPress by [Oren Yomtov](http://orenyomtov.com/). It makes it easy to extend the Post Editor without needing to resort to hacking `quicktags.js`.
One tiny drawback: sometimes I have character entity mismatches. Quicktags for special characters, such as ‘é’ , ‘–‘ , ‘…’, work until the next time I add a quicktag via the PEB interface, when they are returned as ‘Ã©’, ‘â��’, ‘â�¦’.