diff --git a/src/utils/normalize-node-and-offset.js b/src/utils/normalize-node-and-offset.js
new file mode 100644
index 000000000..0427a6ea6
--- /dev/null
+++ b/src/utils/normalize-node-and-offset.js
@@ -0,0 +1,81 @@
+
+/**
+ * From a DOM selection's `node` and `offset`, normalize so that it always
+ * refers to a text node.
+ *
+ * @param {Element} node
+ * @param {Number} offset
+ * @return {Object}
+ */
+
+function normalizeNodeAndOffset(node, offset) {
+  // If it's an element node, its offset refers to the index of its children
+  // including comment nodes, so convert it to a text equivalent.
+  if (node.nodeType == 1) {
+    const isLast = offset == node.childNodes.length
+    const direction = isLast ? 'backward' : 'forward'
+    const index = isLast ? offset - 1 : offset
+    node = getNonComment(node, index, direction)
+
+    // If the node is not a text node, traverse until we have one.
+    while (node.nodeType != 3) {
+      const i = isLast ? node.childNodes.length - 1 : 0
+      node = getNonComment(node, i, direction)
+    }
+
+    // Determine the new offset inside the text node.
+    offset = isLast ? node.textContent.length : 0
+  }
+
+  // Return the node and offset.
+  return { node, offset }
+}
+
+/**
+ * Get the nearest non-comment to `index` in a `parent`, preferring `direction`.
+ *
+ * @param {Element} parent
+ * @param {Number} index
+ * @param {String} direction ('forward' or 'backward')
+ * @return {Element|Null}
+ */
+
+function getNonComment(parent, index, direction) {
+  const { childNodes } = parent
+  let child = childNodes[index]
+  let i = index
+  let triedForward = false
+  let triedBackward = false
+
+  while (child.nodeType == 8) {
+    if (triedForward && triedBackward) break
+
+    if (i >= childNodes.length) {
+      triedForward = true
+      i = index - 1
+      direction = 'backward'
+      continue
+    }
+
+    if (i < 0) {
+      triedBackward = true
+      i = index + 1
+      direction = 'forward'
+      continue
+    }
+
+    child = childNodes[i]
+    if (direction == 'forward') i++
+    if (direction == 'backward') i--
+  }
+
+  return child || null
+}
+
+/**
+ * Export.
+ *
+ * @type {Function}
+ */
+
+export default normalizeNodeAndOffset
diff --git a/src/utils/offset-key.js b/src/utils/offset-key.js
index 3ead33865..39fc9957c 100644
--- a/src/utils/offset-key.js
+++ b/src/utils/offset-key.js
@@ -1,4 +1,6 @@
 
+import normalizeNodeAndOffset from './normalize-node-and-offset'
+
 /**
  * Offset key parser regex.
  *
@@ -46,44 +48,30 @@ function findBounds(index, ranges) {
 }
 
 /**
- * From a `element`, find the closest parent's offset key.
+ * From a DOM node, find the closest parent's offset key.
  *
- * @param {Element} element
- * @param {Number} offset
+ * @param {Element} rawNode
+ * @param {Number} rawOffset
  * @return {Object}
  */
 
-function findKey(element, offset) {
-  if (element.nodeType == 3) element = element.parentNode
+function findKey(rawNode, rawOffset) {
+  let { node, offset } = normalizeNodeAndOffset(rawNode, rawOffset)
 
-  const parent = element.closest(SELECTOR)
-  const children = element.querySelectorAll(SELECTOR)
+  // Find the closest parent with an offset key attribute.
+  const closest = node.parentNode.closest(SELECTOR)
   let offsetKey
 
-  // Get the key from a parent if one exists.
-  if (parent) {
-    offsetKey = parent.getAttribute(ATTRIBUTE)
+  // Get the key from the closest matching node if one exists.
+  if (closest) {
+    offsetKey = closest.getAttribute(ATTRIBUTE)
   }
 
-  // COMPAT: In Firefox, and potentially other browsers, when performing a
-  // "select all" action, a parent element is selected instead of the text. In
-  // this case, we need to select the proper inner text nodes. (2016/07/26)
-  else if (children.length) {
-    let child = children[0]
-
-    if (offset != 0) {
-      child = children[children.length - 1]
-      offset = child.textContent.length
-    }
-
-    offsetKey = child.getAttribute(ATTRIBUTE)
-  }
-
-  // Otherwise, for void node scenarios, a cousin element will be selected, and
+  // Otherwise, for void node scenarios, a cousin node will be selected, and
   // we need to select the first text node cousin we can find.
   else {
-    while (element = element.parentNode) {
-      const cousin = element.querySelector(SELECTOR)
+    while (node = node.parentNode) {
+      const cousin = node.querySelector(SELECTOR)
       if (!cousin) continue
       offsetKey = cousin.getAttribute(ATTRIBUTE)
       offset = cousin.textContent.length
@@ -93,12 +81,11 @@ function findKey(element, offset) {
 
   // If we still didn't find an offset key, error. This is a bug.
   if (!offsetKey) {
-    throw new Error(`Unable to find offset key for ${element} with offset "${offset}".`)
+    throw new Error(`Unable to find offset key for ${node} with offset "${offset}".`)
   }
 
-  // Parse the offset key.
+  // Return the parsed the offset key.
   const parsed = parse(offsetKey)
-
   return {
     key: parsed.key,
     index: parsed.index,