Anyway, as Unknown Bliss said, development processes and mentalities have changed since that was added. At the point, at least how I see it, features should be scrutinized based not only on their practicality in general, but also on their applicability to the phpBB admin community at large, rather than a small subset of people who actually do programming or need to post different types of code.
That being said, I disagree with DavidIQ about removing the PHP highlighting. In my opinion, people have come to expect it. And for those who are upgrading 3.0 to 3.1, what do we do with the existing "code=php"? Just ignore it and treat it as normal? That would just bring up a lot of confusion and unhappiness from those who have used it. And I like it.