Currently, if you duplicate a TextBlock not featuring any runs, it duplicates and renders as expected immediately.

However, if you perform the same duplication operation on a TextBlock featuring Runs, it duplicates, but does not render on the Page until the Page is closed and re-opened.

See attached video showing a comparison of both instances.

Repro Steps:

1) Create a Studio Project featuring a MainPage.xaml.

2) Introduce a StackPanel to the Page

3) Introduce a TextBlock to the StackPanel from Step 2), and type in multiple words into its 'Text' Property.

4) Double-click on the TextBlock on the Stage, and click-and-drag over one of the words to select it, then press the (+) icon in the Text Adorner to make it into a Run.

5) Repeat the process with any other further words or spaces.

6) Select the TextBlock containing the Runs, and duplicate it within the StackPanel.

Observe how the duplicated TextBlock doesn't render on-Page despite occupying a footprint.
Observe how the TextBlock's name in the Navigator has been wiped.

7) Save all open documents, and re-open MainPage.xaml

Observe how the duplicated TextBlock containing runs now renders as expected.
Observe how the duplicated TextBlock has now regained its name in the Navigator.

Expected Results: Duplicated TextBlocks containing runs render immediately upon duplication, and are given the correct names in the Navigator.