Building a new template? Using placeholder links? Office 365 giving you grief?

The problem

Text appears to randomly ignore styling in Office 365 (ie. font-size, font-family, color, line-height).

The cause

The problem appears to be caused by placeholder links in the template, but it doesn't always happen. The Office 365 preprocessor is clearly doing something funky.
It is a mystery

The solution

You just have to use well formed placeholder links when testing your template:

Don't do this

<a>
<a href="">
<a href="#">
<a href="$MERGE_TAG$">
<a href="And then">

Do this

<a href="#top">
<a href="http://www.bing.com/">
<a href="http://any.well.formed/link">

Example code that breaks in Office 365. The <p> tag reverts to default font styles.

<h1 style="Margin: 20px 0; line-height: 100%; font-family: Helvetica Neue, Arial, sans-serif; font-size: 56px; font-weight: bold; color: #424242">
    <a href="#" style="line-height: 100%; text-decoration: none; color: #424242">Heading</a>
</h1>
<p style="Margin: 20px 0; line-height: 122%; font-family: Helvetica Neue, Arial, sans-serif; font-size: 22px; color: #424242">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus cursus purus quis
    tellus adipiscing sit amet suscipit justo malesuada.
</p>

Simply changing the href to #top fixes it. Nesting the font styles inside the <p> tag also fixes it, but wasn't what I needed (ie, <p><span style="font styles here"></span></p>).

As you can see, this only really presents itself as a problem when building a template, since you wouldn't deploy a campaign with empty links.

Edit: This problem is related.