JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdn.ckeditor.com/4.7.0/standard/ckeditor.js"></script>
<textarea id="ck">
  <div>
  Hello
  </div>
  <br/><br/>
  <div>
  world
  </div>
</textarea>

JavaScript

var editor = CKEDITOR.replace('ck', {
    allowedContent: true,
    enterMode: CKEDITOR.ENTER_BR
});

editor.on( 'pluginsLoaded', function( evt ){
	evt.editor.dataProcessor.dataFilter.addRules({
		elements :{
			br : function( element ) {			
				//if next element is BR or <!--cke_br_comment-->, ignore it.
				if( element && element.next && ( element.next.name == 'br' || element.next.value == 'cke_br_comment' ) ){
					return;
				}else {
					var comment = new CKEDITOR.htmlParser.comment( 'cke_br_comment' );
					comment.insertAfter( element );	
				}
			}
		}
	});
				
	evt.editor.dataProcessor.htmlFilter.addRules({
		comment : function( value, node ) {
			if( value.indexOf('cke_br_comment') >= 0 ) {
				return false;
			}
		}
	});
				
});