A fresh install on latest version of joomla. Created a new Disqus account for this.

Do see a "comments" line, which goes blank on mouse over, but activates a new window on click, but, there is no mention of disqus and no where is seen to add comments.

I thought I followed the directions precisely.

OK. so entering the short name as www-mysite-com, seemed to resolve the no Disqus issue. Still no idea where to look to change the disappearing text on mouse over, though.

The issue was resolved by using the FireFox "debugger" (F12) and figuring out where the formatting for the comments text "button" was for the template I was using. Changed the background color (IIRC) and the disappearing text on mouse over ceased. Not a Disqus issue at all it turned out.