When posting a link that has already been posted, give the submitter the option to just bump the old topic to the top of the activity sort
Building off #181 (closed) , when a user enters a link into the topic submission form, they should be greeted with the option to review older topics containing this link and bump one of those older topics instead of reposting a new topic.
Example:
https://tild.es/f2o (now removed) was a repost of https://tild.es/et3
In this example, the submitter could have been made aware that another topic with the same link was posted seven days ago and been given the option to just bump the old topic, perhaps with an entry added to the topic log in the sidebar explaining who bumped the topic.