1. A way to 'unlist' posts
A while back I wrote a post about a new system of utilitarianism that in retrospect was kinda bad. Later I wrote a different post with a new system that expanded on the old idea and that was generally better in every single way. Now I had the dilemma of what to do with the old post. I want this site to exhibit quality posts which the old one wasn't, but I also want to document my thought process and have an archive of how ideas evolved. I compromised by deleting the old post but having a link to a pdf-file of the old idea in the new post.
A possible middle-ground would be a feature similar to youtube's 'unlisting'. The link to the post still works so it's all still documented and you can link to it if you want, but it doesn't directly show up in the search results. This will make your personal page (and LW in general) more 'cleaned up'.
2. Strikethrough and/or Retracting posts
You can retract comments with a simple click of the button but not posts, why? You can manually edited your post and use strikethrough to cross stuff out, but it is not readily available to you and you'll have to search the site to find out how to do that (it's two '~' before and two '~' after a word). Even then it is not easy to get rid of a strikethrough once you added it. None of these are impossible hurdles to jump over, but why should there be any hurdles at all?
3. A way to delete a tag
On one post I accidentally added a tag that was not really relevant to post. I wanted to delete the tag but found out it was impossible. Maybe a way to delete a tag that you yourself added (and no-one else agrees with) could prevent cluttered and/or wrong tags on posts?
EDIT: I will add one microscopic nitpick to the list. A small spelling error: