Aha, yep. Count me among those people who are confused. Thanks for pointing me in the right direction, @threadi.
I think the original post is asking about highlighting for the post editor.
You may have more luck using Greasemonkey user scripts, since there doesn’t seem to be a demand for a plugin like this. (See also)
Possibly this: Contact Form 7 Dynamic Text Extension.
There also seem to be some ideas here, but they seem to involve hacking at the Contact Form 7 code, which most people will tell you is inadvisable (you lose your changes when the plugin gets updated).
I have to do the same thing with an online (animal) adoptions application. If have any great revelations in the process, I’ll post a follow-up here.