I think they grey out of dead comments is a feature. It lets you read them if you want, but is a huge visual indicator that it isn't worth reading.
Remember, people who do not want to read any dead comments will have left "showdead" in its default state of "off", and so won't see these at all. The only people who see dead comments are those who explicitly said they want to see them.
You can test it on the comments on this submission: https://news.ycombinator.com/item?id=11213213
There are several dead comments near the bottom that are visible if showdead is "yes", and invisible if it is "no".