Funny thing about that episode where they edited some of Race's dialog is that while the audio is muted, the full dialog is in the subtitles (from what I've read, I haven't had a chance to watch my DVD set yet). Not only that, the episodes run on Boomerang completely unedited; none of DVDs' audio edit[s] nor the scene edits that led to years of butchered action sequences starting in the 70s.
I watched part of the documentary MekaGojira3k posted the link too; it mentions another bit of edited dialog in a different episode. I believe it's "Monster in the Monastery" -- after Jonny causes an armed bad guy to slip on the stairs he dodges the villain while saying "Here comes the Orient Express".
They talk about the DVD edits in part 13:
http://www.youtube.com/watch?v=QkAtLP1qmho
In another section of the documentary, they mention that WBHV screwed up the closing credits on most of the episodes. From what I've read, WBHV pulled a similar screw-up with their release of the Fleischer Studios (and technically Famous Stuidos after Paramount assumed control) Superman theatrical cartoons.
If there's ever a quality Blu-Ray release of Jonny Quest I hope someone at WBHV makes sure the episodes are fully restored (at least as far as audio and closing credits). {not to mention other screw-ups on other releases}