FIX: Don't warn users about duplicate links for:

- The original post
- If the post is older than (x) (Two Weeks for now)

app/assets/javascripts/discourse/controllers/composer.js.es6

@@ -228,8 +228,6 @@ export default Ember.Controller.extend({
       if (topic.get('posts_count') === 1) { return; }
 
       const post = this.get('model.post');
-      if (post && post.get('user_id') !== this.currentUser.id) { return; }
-
       const $links = $('a[href]', $preview);
       $links.each((idx, l) => {
         const href = $(l).prop('href');

app/assets/javascripts/discourse/lib/link-lookup.js.es6

@@ -1,5 +1,4 @@
 const _warned = {};
-
 const NO_RESULT = [false, null];
 
 export default class LinkLookup {
@@ -16,8 +15,18 @@ export default class LinkLookup {
 
     const linkInfo = this._links[normalized];
     if (linkInfo) {
-      // Skip edits to the same post
-      if (post && post.get('post_number') === linkInfo.post_number) { return NO_RESULT; }
+
+      if (post) {
+        // Skip edits to the OP
+        const postNumber = post.get('post_number');
+        if (postNumber === 1) { return NO_RESULT; }
+
+        // Don't warn on older posts
+        const createdAt = moment(post.get('created_at'));
+        if (createdAt.isBefore(moment().subtract(2, 'weeks'))) {
+          return NO_RESULT;
+        }
+      }
 
       _warned[href] = true;
       _warned[normalized] = true;