more robust title element detection

Author: cscheid

src/format/html/format-html-title.ts

@@ -210,13 +210,33 @@ export async function canonicalizeTitlePostprocessor(
     const h1s = Array.from(doc.querySelectorAll("h1"));
     for (const h1n of h1s) {
       const h1 = h1n as Element;
-      if (!h1.classList.contains("quarto-secondary-nav-title")) {
-        const div = doc.createElement("div");
-        div.classList.add("quarto-title-banner");
-        h1.classList.add("title");
-        header.appendChild(h1);
-        break;
+      if (h1.classList.contains("quarto-secondary-nav-title")) {
+        continue;
       }
+
+      // Now we need to check whether this is a plausible title element.
+      if (h1.parentElement?.tagName === "SECTION") {
+        // If the parent element is a section, then we need to check if there's
+        // any content before the section. If there is, then this is not a title
+        if (
+          h1.parentElement?.parentElement?.firstElementChild !==
+            h1.parentElement
+        ) {
+          continue;
+        }
+      } else {
+        // If the parent element is not a section, then we need to check if there's
+        // any content before the h1. If there is, then this is not a title
+        if (h1.parentElement?.firstElementChild !== h1) {
+          continue;
+        }
+      }
+
+      const div = doc.createElement("div");
+      div.classList.add("quarto-title-banner");
+      h1.classList.add("title");
+      header.appendChild(h1);
+      break;
     }
   }