I like the recent Highlight feature that's been available since version 1.0.4 (for some reason only available as a download from the author's GitHub page), but it has one side-effect that has a massive potential of breaking websites. The highlight is not only applied to visible text within tags, but to the whole page ( document.body.innerHTML ). This can break inline JavaScript, link references and all kinds of other things as well if a match is found, which sadly makes it unusable as the multi-word highlighter that I've been looking for.

For other use cases, such as extracting data from the page source, it's a neat extension but I have no such requirements myself.