def get_comment_value(node, name, field):
    """Get the value of a comment field.

    :sig: (SpecNode, str, str) -> str
    :param node: Node to get the comment from.
    :param name: Name of setting in the node.
    :param field: Name of comment field.
    :return: Value of comment field.
    """
    try:
        comment = node.ca.items[name][2].value[1:].strip()
    except KeyError:
        comment = None
    if comment is not None:
        delim = field + ':'
        if comment.startswith(delim):
            return comment[len(delim):].strip()
    return None
