The author of a page can name their CSS classes anything they choose, and for some reason they chose the name "hiddenH1Text" for this class. What this class actually means is defined elsewhere - either in an external .css file or in the <head> area.
It would be rather foolish to try to game search engines with hidden text and then advertise the fact so boldly right in the code. Then again, people do foolish things.
In all fairness - although I fought it tooth and nail - it may just be the design. I just completed a project with "tabs" on all the pages and the tabs appeared right under the header stuff.
No visible h1. <gasp>
So when the SEO people approached the project, they're thinking "what the heck, what are you thinking?" We put some in with exactly that approach . . . also sticking poorly in my craw.
You've opened a good question though. When, for whatever reason, an h1 is set to display:none, is this considered "hidden content" by the S.E.'s, and does it inflict their wrath, especially if the h1 in question is both relevant and non-stuffed?
Alternatively, an image-based h1, which I doubt is the same environment because the h1 content is similar or identical to the graphic content.
As I think a tag alone has no value whenever there is no data into it. If there were some text in the h1 tag and it become hidden it may be considered as BLACK HAT, but if there is nothing i think it may be just a mistake.