diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
index eaa9029..57df41c 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
@@ -49,7 +49,9 @@
   BlameInfo,
   ChangeInfo,
   CommentRange,
+  EditPatchSetNum,
   NumericChangeId,
+  ParentPatchSetNum,
   PatchRange,
   PatchSetNum,
   RepoName,
@@ -752,7 +754,7 @@
       side === Side.LEFT && isAParent(this.patchRange.basePatchNum)
         ? CommentSide.PARENT
         : CommentSide.REVISION;
-
+    if (!this.canCommentOnPatchSetNum(patchNum)) return;
     const threadEl = this._getOrCreateThread(
       patchNum,
       lineNum,
@@ -766,6 +768,32 @@
     this.reporting.recordDraftInteraction();
   }
 
+  private canCommentOnPatchSetNum(patchNum: PatchSetNum) {
+    if (!this._loggedIn) {
+      fireEvent(this, 'show-auth-required');
+      return false;
+    }
+    if (!this.patchRange) {
+      fireAlert(this, 'Cannot create comment. patchRange undefined.');
+      return false;
+    }
+
+    const isEdit = patchNum === EditPatchSetNum;
+    const isEditBase =
+      patchNum === ParentPatchSetNum &&
+      this.patchRange.patchNum === EditPatchSetNum;
+
+    if (isEdit) {
+      fireAlert(this, 'You cannot comment on an edit.');
+      return false;
+    }
+    if (isEditBase) {
+      fireAlert(this, 'You cannot comment on the base patchset of an edit.');
+      return false;
+    }
+    return true;
+  }
+
   /**
    * Gets or creates a comment thread at a given location.
    * May provide a range, to get/create a range comment.
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_html.ts b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_html.ts
index a7eebf4..9d5555d 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_html.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_html.ts
@@ -21,7 +21,6 @@
     id="diff"
     change-num="[[changeNum]]"
     no-auto-render="[[noAutoRender]]"
-    patch-range="[[patchRange]]"
     path="[[path]]"
     prefs="[[prefs]]"
     display-line="[[displayLine]]"
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
index db0b65a..99486ad 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
@@ -26,6 +26,7 @@
 import {CoverageType} from '../../../types/types.js';
 import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 import {createDefaultDiffPrefs} from '../../../constants/constants.js';
+import {EditPatchSetNum, ParentPatchSetNum} from '../../../types/common.js';
 
 const basicFixture = fixtureFromElement('gr-diff-host');
 
@@ -659,6 +660,30 @@
     });
   });
 
+  test('cannot create comments when not logged in', () => {
+    element.patchRange = {
+      basePatchNum: 'PARENT',
+      patchNum: 2,
+    };
+    const showAuthRequireSpy = sinon.spy();
+    element.addEventListener('show-auth-required', showAuthRequireSpy);
+
+    element.dispatchEvent(new CustomEvent('create-comment', {
+      detail: {
+        lineNum: 3,
+        side: Side.LEFT,
+        path: '/p',
+      },
+    }));
+
+    const threads = dom(element.$.diff)
+        .queryDistributedElements('gr-comment-thread');
+
+    assert.equal(threads.length, 0);
+
+    assert.isTrue(showAuthRequireSpy.called);
+  });
+
   test('delegates cancel()', () => {
     const stub = sinon.stub(element.$.diff, 'cancel');
     element.patchRange = {};
@@ -789,12 +814,6 @@
     assert.equal(element.$.diff.noAutoRender, value);
   });
 
-  test('passes in patchRange', () => {
-    const value = {patchNum: 'foo', basePatchNum: 'bar'};
-    element.patchRange = value;
-    assert.equal(element.$.diff.patchRange, value);
-  });
-
   test('passes in path', () => {
     const value = 'some/file/path';
     element.path = value;
@@ -949,6 +968,12 @@
   });
 
   suite('create-comment', () => {
+    setup(async () => {
+      loggedIn = true;
+      element.attached();
+      await flush();
+    });
+
     test('creates comments if they do not exist yet', () => {
       const diffSide = Side.LEFT;
       element.patchRange = {
@@ -1147,6 +1172,50 @@
       assert.equal(threads[0].diffSide, diffSide);
       assert.equal(threads[0].path, element.file.path);
     });
+
+    test('cannot create thread on an edit', () => {
+      const alertSpy = sinon.spy();
+      element.addEventListener('show-alert', alertSpy);
+
+      const diffSide = Side.LEFT;
+      element.patchRange = {
+        basePatchNum: EditPatchSetNum,
+        patchNum: 3,
+      };
+      element.dispatchEvent(new CustomEvent('create-comment', {
+        detail: {
+          side: diffSide,
+          path: '/p',
+        },
+      }));
+
+      const threads = dom(element.$.diff)
+          .queryDistributedElements('gr-comment-thread');
+      assert.equal(threads.length, 0);
+      assert.isTrue(alertSpy.called);
+    });
+
+    test('cannot create thread on an edit base', () => {
+      const alertSpy = sinon.spy();
+      element.addEventListener('show-alert', alertSpy);
+
+      const diffSide = Side.LEFT;
+      element.patchRange = {
+        basePatchNum: ParentPatchSetNum,
+        patchNum: EditPatchSetNum,
+      };
+      element.dispatchEvent(new CustomEvent('create-comment', {
+        detail: {
+          side: diffSide,
+          path: '/p',
+        },
+      }));
+
+      const threads = dom(element.$.diff)
+          .queryDistributedElements('gr-comment-thread');
+      assert.equal(threads.length, 0);
+      assert.isTrue(alertSpy.called);
+    });
   });
 
   test('_filterThreadElsForLocation with no threads', () => {