diff --git a/src/content/definition-engine.ts b/src/content/definition-engine.ts
index 02b4476..7adebc2 100644
--- a/src/content/definition-engine.ts
+++ b/src/content/definition-engine.ts
@@ -78,7 +78,7 @@ export class DefinitionEngine {
       const matches = Array.from(post.querySelectorAll(selector));
       const contents = post.matches(selector) ? [post, ...matches] : matches;
       for (const content of contents) {
-        const text = visibleText(content, this.definition.post.excludedSelectors ?? []);
+        const text = visibleText(content, this.definition.post.excludedSelectors ?? [], post);
         if (text) return text;
       }
     }
@@ -140,13 +140,19 @@ function wildcardMatches(pattern: string, value: string): boolean {
 
 function escapeRegex(value: string): string { return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"); }
 
-function visibleText(element: Element, excludedSelectors: string[]): string {
+function visibleText(element: Element, excludedSelectors: string[], postBoundary: Element): string {
   const chunks: string[] = [];
   const walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT);
   let node: Node | null;
   while ((node = walker.nextNode())) {
     const parent = node.parentElement;
-    if (!parent || excludedSelectors.some((selector) => parent.closest(selector))) continue;
+    // An excluded container only applies when it is inside this post's
+    // boundary. Nested Reddit comments are themselves inside an ancestor
+    // `.child` container, which must not exclude the comment's own text.
+    if (!parent || excludedSelectors.some((selector) => {
+      const excluded = parent.closest(selector);
+      return excluded !== null && postBoundary.contains(excluded);
+    })) continue;
     if (isVisible(parent, element)) chunks.push(node.textContent ?? "");
   }
   return normalizeText(chunks.join(" "));
diff --git a/src/content/definitions/default.json b/src/content/definitions/default.json
index a2fd27b..b0f8934 100644
--- a/src/content/definitions/default.json
+++ b/src/content/definitions/default.json
@@ -44,12 +44,12 @@
         "https://old.reddit.com/*"
       ],
       "requiredSelectors": [
-        "#siteTable .thing.link, #siteTable .thing.comment"
+        "#siteTable .thing.link, .commentarea .thing.comment > .entry"
       ],
       "post": {
         "rootSelectors": [
           "#siteTable > .thing.link",
-          "#siteTable .thing.comment"
+          ".commentarea .thing.comment > .entry"
         ],
         "textSelectors": [
           ".md",
diff --git a/src/content/definitions/sites/reddit-old.json b/src/content/definitions/sites/reddit-old.json
index a7998a8..00c4efd 100644
--- a/src/content/definitions/sites/reddit-old.json
+++ b/src/content/definitions/sites/reddit-old.json
@@ -2,9 +2,9 @@
   "id": "reddit-old",
   "name": "Reddit (old interface)",
   "urlPatterns": ["https://old.reddit.com/*"],
-  "requiredSelectors": ["#siteTable .thing.link, #siteTable .thing.comment"],
+  "requiredSelectors": ["#siteTable .thing.link, .commentarea .thing.comment > .entry"],
   "post": {
-    "rootSelectors": ["#siteTable > .thing.link", "#siteTable .thing.comment"],
+    "rootSelectors": ["#siteTable > .thing.link", ".commentarea .thing.comment > .entry"],
     "textSelectors": [".md", ".title"],
     "excludedSelectors": [".expando", ".child"],
     "idAttributes": ["data-fullname"],
diff --git a/tests/definition-engine.test.ts b/tests/definition-engine.test.ts
index c0708cc..bb065d9 100644
--- a/tests/definition-engine.test.ts
+++ b/tests/definition-engine.test.ts
@@ -95,12 +95,35 @@ describe("DefinitionEngine", () => {
     expect(posts.map((post) => post.text)).toEqual(["the main post on the threads detail page", "a reply on the threads detail page"]);
   });
 
-  it("discovers posts from the old Reddit interface using fullname IDs", () => {
+  it("discovers old Reddit posts and comment entries from their separate page containers", () => {
     document.body.innerHTML = readFileSync("tests/fixtures/reddit-old-feed.html", "utf8");
     const reddit = BUILTIN_DEFINITIONS.find((candidate) => candidate.id === "reddit-old")!;
     const posts = new DefinitionEngine(reddit).discover(document);
-    expect(posts.map((post) => post.id)).toEqual(["reddit-old:t3_abc123", "reddit-old:t1_def456"]);
-    expect(posts.map((post) => post.text)).toEqual(["the post body with visible text.", "a useful comment with visible text."]);
+    expect(posts.map((post) => post.id)).toEqual([
+      "reddit-old:t3_abc123",
+      "reddit-old:https://old.reddit.com/r/example/comments/abc123/example_post/def456/",
+      "reddit-old:https://old.reddit.com/r/example/comments/abc123/example_post/ghi789/"
+    ]);
+    expect(posts.map((post) => post.text)).toEqual([
+      "the post body with visible text.",
+      "a useful comment with visible text.",
+      "a nested reply with its own visible text."
+    ]);
+  });
+
+  it("discovers old Reddit comment entries appended after observation starts", async () => {
+    document.body.innerHTML = readFileSync("tests/fixtures/reddit-old-feed.html", "utf8");
+    const reddit = BUILTIN_DEFINITIONS.find((candidate) => candidate.id === "reddit-old")!;
+    const engine = new DefinitionEngine(reddit);
+    const observed: string[] = [];
+    const stop = engine.observe((posts) => observed.push(...posts.map((post) => post.text)));
+    const comment = document.createElement("div");
+    comment.className = "thing comment";
+    comment.innerHTML = '<div class="entry"><div class="md"><p>A newly loaded reply.</p></div><a class="bylink" href="/r/example/comments/abc123/example_post/jkl012/">permalink</a></div>';
+    document.querySelector(".commentarea .sitetable")?.append(comment);
+    await new Promise((resolve) => setTimeout(resolve, 0));
+    stop();
+    expect(observed).toContain("a newly loaded reply.");
   });
 
   it("discovers X posts using semantic tweet markers and permalink IDs", () => {
diff --git a/tests/fixtures/reddit-old-feed.html b/tests/fixtures/reddit-old-feed.html
index b28e289..78c0d6a 100644
--- a/tests/fixtures/reddit-old-feed.html
+++ b/tests/fixtures/reddit-old-feed.html
@@ -3,7 +3,16 @@
     <p class="title"><a class="title" href="https://old.reddit.com/r/example/comments/abc123/example_post/">A useful Reddit post</a></p>
     <div class="entry"><div class="expando"><div class="md">Hidden expanded media controls</div></div><div class="md"><p>The post body with visible text.</p></div></div>
   </div>
-  <div class="thing comment" data-fullname="t1_def456">
-    <div class="entry"><div class="md"><p>A useful comment with visible text.</p></div><a class="bylink" href="https://old.reddit.com/r/example/comments/abc123/example_post/def456/">permalink</a></div>
+</div>
+<div class="commentarea">
+  <div class="sitetable nestedlisting">
+    <div class="thing comment" data-fullname="t1_def456">
+      <div class="entry"><div class="md"><p>A useful comment with visible text.</p></div><a class="bylink" href="https://old.reddit.com/r/example/comments/abc123/example_post/def456/">permalink</a></div>
+      <div class="child">
+        <div class="thing comment" data-fullname="t1_ghi789">
+          <div class="entry"><div class="md"><p>A nested reply with its own visible text.</p></div><a class="bylink" href="https://old.reddit.com/r/example/comments/abc123/example_post/ghi789/">permalink</a></div>
+        </div>
+      </div>
+    </div>
   </div>
 </div>