Content can only be edited or updated by an author for up-to 3 hours after initially posting topics or comments. If you would like to edit after that point please contact a moderator or administrator to help you. If there is already a string of comments after you have initially posted, it is best to revise your content in a follow-up comment.
The reason for edit-restrictions is because comments follow the initial topic statement and string of comments. Subsequent comments may not make sense if edits were allowed indefinitely.