Can you go in the settings to the tempalte tab and disable minify and merge. This would output the js file as they are and we could get a better idea from where exactly in the code the error is coming.
Ok, I think I know what is going on, but you have to figure out what you've turned on your site that does this.
When we send an ajax request to save the comment - the response instead of a json with the comment is:
<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="/https://www.googletagmanager.com/gtag/js?id=xxxx"></script>
window.dataLayer = window.dataLayer || ;
gtag('js', new Date());
<tr><td><p>Hier komt binnenkort de nieuwe website van<br>
Bergen Limburg Online
Are you using a google analytics plugin? Can yuo disable it and see if it works afterwards. This is an html response and it shouldn't be there. This shouldn't be triggered when we request a json response.
Do you have an index.html file on the website?
Our request is pointing to http://yourdomain.com/?option=com_comment&task=comments.getcomments&format=json&lang=en&contentid=91&component=com_content&start=1
this leads to. white page with the text
Hier komt binnenkort de nieuwe website van
and the mentioned analytics code.
If I do a request to index.php?... then I get the expected result. If you do have an index.html - remoe it and it should start to work.