I'm new to Disqus and have just added it to my blog site.
However, I've noticed that upon Disqus loading via JavaScript, it adds a hashtag to the page’s URL:
Why is this? Is there a setting to opt-out of it?
Are you sure Disqus is adding it ?
It's some kind of stat tracking hashtag and I am a bit sure it is by AddThis (might be some other site too). If you have AddThis share widget on your web page then you probably have enabled tracking for it, to get rid of it just remove this line of code from the AddThis snippet :
<script type="text/javascript">var addthis_config = {"data_track_addressbar":true};</script>