There is no option to delete your comment on any cf post. Generally there's no problem because it forces you to think before commenting and prevent any immature comment. But problem occurs when someone edit there blog totally and now your comment not only seems to weird but also stupid on that blog. Though you can edit your comment but sometimes you find nothing relevant to say on that new topic.
So I want to say that if writer of a blog edits his/her blog then there should be an option to delete comment for all who comment before editing that blog.
I think blogs should also have a complete edit log just like comments do. Deleting comments (and blogs for that matter) should only be possible for moderators for abusive content.
I don't want that power to delete other people's comments on my post. I said that I should be able to delete my comment when blogger change his/her blog completely after read my comment.
I never said you should have that power.
You can edit your comment to something like "does not apply because blog changed". The changelog for blogs is available so everyone will understand what happened. There is no need to delete such comment.
Blog authors have an option to make edit history invisible to the public.