I'm not sure that term frequency is the right way to go about the problem of clickbait. Frequently, titles and body text is meant to match up as a form of SEO.

I'm not sure if this can be done through an extension, but an alternative way to go about this is by measuring time spent on the page. If the page has X words which takes Y minutes to read, but a certain number of people bounce before that time, the score is lowered. The more users that stay on the page for Y minutes, the higher the score.

There are a lot of assumptions in that solution, but it might be worth considering.