What you're asking for would basically require a complete rewrite of the channel (and query) display windows. I really don't think there's enough benefit to make that worth doing. Most ignore systems out there are just like this one... if ignored, the person is entirely ignored. And people are used to them. With the amount of work required, I don't think it's going to happen.
That said, I think there are some feature requests that have come in over time that would also require rewriting some or all of the display system for channels/queries. If Khaled decides to tackle those, then including this at the same time might be an option.
In the meantime, Wims's idea of just using the same foreground and background colors on the text would accomplish the same thing. You would just highlight the text instead of "expanding" it. It's also a fairly easy thing to script and you can add a variety of options to personalize it that wouldn't necessarily be available from a built-in feature.