Thank you for contacting Syncfusion support.
We were able to replicate the reported issue in our end and we are considering this as a defect. The fix for this issue will be included in our upcoming 2018 Volume 4 release. Meanwhile, we can access the RTE’s value from the value property using the instance which can be obtained as demonstrated in the following code.
// ‘new comment’ is the ID attribute, you need to append ‘-value’ at the end.
var rteObj = document.getElementById('newComment' + '-value').ej2_instances;
Please note the above workaround solution will work only till this issue is fixed (i.e.) till 2018 volume 4 release. After the fix you can take the instance directly using the ID attribute.