Comment on SEO Recent Posts WordPress Widget by SEO Dave.

WordPress Popular Posts Widget Options WordPress strips code in comments, to post code you have to add it to code tags

<code>CODE Here</code>

To center something in the widget you’ll need to add HTML code that centers it.

Stallion includes several CSS classes which center code for example:

<div class="align-center">
Your code here

If the above was added by default to the Single Posts Widget it would prevent using the widget for left aligned and right aligned content.