>>12

var start = document.evaluate('.//comment()[contains(., "start")]', document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
var end = document.evaluate('.//comment()[contains(., "end")]', document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
var range = document.createRange();

var startNode = start.snapshotItem(0);
var endNode = end.snapshotItem(0);
range.setStartAfter(startNode);
range.setEndBefore(endNode);
range.deleteContents();