I think we also need this to support superscript/subscript text on TextBlock.
If there is workaround, please let us know.

As a workaround you can use a InlineUIContainer containing a TextBlock with the appropriate size and margin:

  <TextBlock FontSize="20" HorizontalAlignment="Center" VerticalAlignment="Center">

<Run Text="Text with"/>

<InlineUIContainer><TextBlock FontSize="12" Text="superscript" Margin="0,-12,0,0"/></InlineUIContainer>

<Run Text="and"/>

<InlineUIContainer><TextBlock FontSize="12" Text="subscript" Margin="0,4,0,0"/></InlineUIContainer>

</TextBlock>

Tried the workaround here. Seems to work for superscript but not the subscript. And somehow I need to add top margin of -20 to make the superscript looks nice.
Please see the attachment.

Capture.PNG (96,186 bytes)   

Capture.PNG (96,186 bytes)   

Please try using a negative bottom margin for the subscript:

<TextBlock FontSize="12" Text="subscript" Margin="0,0,0,-10"/>

I have to check why our InlineUIContainers are not behaving like WPF regarding to the margins.

Thanks. Negative bottom margin seems to work.

Capture-2.PNG (54,763 bytes)   

Capture-2.PNG (54,763 bytes)   

Would also be very keen on this feature for showing icons and tooltips in our localized text.

I'm also interested in this feature. The negative margin works well but finding the perfect value is not easy and depends on the font size.