If a story has a lower score due to typoze and grammer, an edit that goes through the story and fixes a lot of them could mean the story is more enjoyable than the score indicates.
Except, scores usually reflect the earliest posted scores. Thus a story that starts strong (or weak) will typically remain in that position indefinitely, with later changes (strong endings, plot twists, etc.) rarely boost the overall scores much). Thus, cleaning up the language doesn't effect the score much. If typos are a major problem for a story, you'd do better deleting the original and reposting the entire thing, so it attracts all new readers and gets a fresh reading (though, of course, then your original readers may vote it down because they didn't like their original scores being erased). :(
Depends? A wrong chapter mis-posting should result in a deletion, which would lower the chapter count, so when a new chapter eventually does get added, it increases the chapter count, and thus triggers the "Updated stories" listing(because a new chapter was added).
Except, that's not how it works. If order to 'delete' a chapter, you typically have to delete the chapter and then wait a full day (or at least several hours to be sure it goes through before posting the update), otherwise the new chapter merely replaces the incorrect chapter.