This is a rather interesting bug! It appears that when the ForumViewThread module processes the page and puts the <link to the RSS feed, the thread title was not passed and escaped through preg_quote_replacement() resulting in a messed up page and HTML syntax:
<link rel="alternate" type="application/rss+xml" title="Posts in the discussion thread "<script type="text/javascript" src="http://d3g0gp89917ko0.cloudfront.net/v--7ec0c0ce32f6/common--modules/js/misc/NewPageHelperModule.js"></script><script type="text/javascript" src="http://d3g0gp89917ko0.cloudfront.net/v--7ec0c0ce32f6/common--modules/js/forum/ForumViewThreadModule.js"></script><script type="text/javascript" src="http://d3g0gp89917ko0.cloudfront.net/v--7ec0c0ce32f6/common--modules/js/forum/ForumViewThreadPostsModule.js"></script></head>"" href="/feed/forum/t-633046.xml"/><script type="text/javascript" src="http://d3g0gp89917ko0.cloudfront.net/v--7ec0c0ce32f6/common--modules/js/misc/NewPageHelperModule.js"></script><script type="text/javascript" src="http://d3g0gp89917ko0.cloudfront.net/v--7ec0c0ce32f6/common--modules/js/forum/ForumViewThreadModule.js"></script><script type="text/javascript" src="http://d3g0gp89917ko0.cloudfront.net/v--7ec0c0ce32f6/common--modules/js/forum/ForumViewThreadPostsModule.js"></script></head>
You can see it reproduced here: http://4free.wikidot.com/forum/t-633046/0-1-2
EDIT: and same goes with this page! It's the same problem! I guess this means that the same problem occurs with the Comments module — but perhaps the Comments module may only be an extension of ForumViewThread…
Thanks for reporting. We fixed this issue.