Will the comment actually disappear completely, or will it just go into a state where nobody else can see it? It seems like it is 1) useful to be able to see your comments that never got endorsed (to let people build a mental model of what makes the cut and what doesn't), and 2) less confusing than just having stuff mysteriously disappear.
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?