Hmm... Now I find myself hoping that I never hit 1000 karma so I won't have to wade through all the never-endorsed comments. Could this feature deter high karma users from logging into the site?

If the quality of "showdead" comments is any indication I don't think you have anything to worry about.

(they are perfectly fine most of the time, their light-greyness is in fact more of an annoyance than the actually quite rare racist slur)