Special characters in question body stop hyperlink working

Question

There is a question whose hyperlink does not work, i.e. the mouse pointer doesn't change when I move it over the question title.
Here is a screen shot:

This is part of the Unanswered Questions list. There are some special characters in the question body, and I presume that it is those that are preventing the hyperlink from working. I know that special characters in the url itself would cause problems, but these are in the question body.

I am using Firefox 13.0.1 on Windows Vista. If I use IE9 there's no problem.

Answer 1

I can confirm that the question link does not react to mousing-over in Firefox 3.6.15 (Windows).

There seems to be absolutely nothing wrong with the HTML source for the link itself:

<div class="summary">        
    <h3><a href="/questions/178726/how-do-i-interpret-the-bellman-equation" class="question-hyperlink">How do I interpret the bellman equation?</a></h3>
    <div class="excerpt">
        Could you interpret this equation?

But something makes Firefox think the first line of the question excerpt is very tall. Here's a screenshot where I've selected the word "you":

So I suppose that when I'm mousing over the question link, Firefox thinks I'm really pointing at the question excerpt, where there's no hyperlink.

After some additional sleuthing: Just before the U+3016 LEFT WHITE LENTICULAR BRACKET (that is, after the (c_t,k_t)) there is an invisible U+2061 FUNCTION APPLICATION. The presence of U+2061 is what makes Firefox think the line extends far above and below the actual visible text.

This looks like a bug in Firefox, not one in the StackExchange server. But I suppose it wouldn't hurt if SE filtered out the "invisible operator" codepoints U+2061 to U+2064 that are now known to cause problems.

I have edited the question to remove the offending character.