Prince produced an incorrect line-break at an in-line MathML element immediately followed by a period (see attached example & code). There seems to be no way to remedy this using CSS. Neither does it help to add a zero-width no-break space (U+2060 word joiner), since it is not recognised by Prince.

Both Firefox and Chrome do not reproduce this error when resizing their view port. However, Firefox appears to have suffered from the same bug a couple of years ago:
https://bugzilla.mozilla.org/show_bug.cgi?id=209693
https://bugzilla.mozilla.org/show_bug.cgi?id=456358

<h1 id="free-space-directivity">Free-space directivity</h1>
<p>The free-space directivity of a log-periodic dipole array (LPDA) is a function of its taper <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>τ</mi></mrow></math> and its chosen spacing <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>σ</mi></mrow></math>.<span class="citation"><sup>1</sup></span> <strong>Decreasing <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>σ</mi></mrow></math> will decrease the boom length <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>L</mi></mrow></math>. Decreasing <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>τ</mi></mrow></math> will decrease both the boom length <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>L</mi></mrow></math> and the number of elements <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>N</mi></mrow></math>.</strong> Because of constrained resources, amateur radio log-periodic antennas often are limited to values of <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>τ</mi></mrow></math> between 0.88 and 0.95, with values of <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>σ</mi></mrow></math> between 0.03 and 0.06.<span class="citation"><sup>2</sup></span></p>

1. mathml.line-break.period.png‎ 54.9 kB ‎
   Example

Edited 31 May 2014 by emperor

We will take a look at this. In the meantime, it might be necessary to wrap the MathML + punctuation inside a non-breaking span (eg. white-space: nowrap).

Just to add my 2 cents: I've encountered this behavior too, and the suggested workaround works. I didn't even know this isn't correct behavior!

It happens with <img>-tags too, I think. Crazy suggestion: maybe add a CSS rule like: "prince-line-break-after: avoid;" ?