Looks like search engine gold to me! but preloaded content might be the spot to consider. Since all we are seeing is what is between those commented lines looks like what a list view would show and the 5,000,000 lines (super long) I bet it is an artifact from the listview.
I wonder if a rel nofollow or a robots.txt file disallow on the listview of topics could sort this out? There are a few spots that listview things so the other thing would be to determine where it is coming from (or are all of them doing this). Example when you go to your profile there is a listview there as well as the main forum listview.
Interesting byproduct. Good catch.
Edit: After my drive to work I got concerned. I don’t know how nofollow or disallow would be a good thing either. We want the search engine to creep into pages like this, correct? So then my thinking is “how on earth do you control this sort of thing”.
So on the one hand you have ‘search engine gold’, on the other hand if Google engineers take a look-see they may scratch their heads and adjust their tools to ‘not’ do this kind of thing.
So then the question becomes. Is it our problem, or Google’s? …and what if anything should we do about it?