Twitter is an amazing thing. Maybe it's not Twitter that's amazing. Maybe it's the people who I know through Twitter that are awesome. Either way, after spending some time with SquareSpace support I couldn't find a simple solution to adding custom formatting to linkposts with this new template. Because of the way SquareSpace works I don't have direct access to the HTML or CSS. However, you can "inject" code to the Header or Footer of the site and add custom CSS.
I appealed on Twitter for some help because I'm very much a novice with HTML and CSS. However, I'm graced to know a number of developers and designers who are not only skilled but also generous. I want to publicly thank everyone who responded to my appeal:
You guys are great!
In the end, I opted to solve the problem with Joe's solution because it was super easy to implement and it worked well with my current needs and limitations.
From now on you will see an icon of a box with an arrow jumping out of it following the title of any linkpost. Hopefully that will clearly indicate to readers that if you click on the post's title it will take you to the external article I'm commenting on in my post.