`undefined` is rendered as ``

[Arcanemagus]

It seems that when `undefined` is in the comment, it is rendered as ``.

Source:

Result:

[Arcanemagus]

Interesting, changing to just undefined makes the word disappear, so the ` aren't actually relevant. Digging deeper...

[Arcanemagus]

donna gives the following for the method in question:

"967": {
  "18": {
    "name": "getMarkerLayer",
    "bindingType": "prototypeProperty",
    "type": "function",
    "paramNames": [
      "id"
    ],
    "range": [
      [
        967,
        18
      ],
      [
        976,
        1
      ]
    ],
    "doc": " Public: Get a {MarkerLayer} by id.\n\n* `id` The id of the marker layer to retrieve.\n\nReturns a {MarkerLayer} or undefined if no layer exists with the given\nid. "
  }
},

So it looks like that isn't the issue.