This patch: 9f362a1 introduced a serious limitation, namely one can not select non-DOMElements. For example, now it is impossible to select only the text content of a specific node, like this: $node->filterXPath('//text()')
The selected node never gets returned because of this:

if ($subNode->nodeType === 1) {
    $crawler->add($subNode);
}

I suggest a solution, where adding non-DOMElements are prevented but selecting one is possible. Is the community open for that? If yes, I am willing to work on it.