noesis:RichText.Text content isn't processed on elements that start with Visibility="Collapsed". When the element later transitions to Visible (e.g. via VisualState storyboard), the RichText inlines never appear to be created and the element renders as empty.

Changing the initial Visibility from Collapsed to Hidden "fixes" it, but it's not ideal.

Works — starts Visible, hidden by VisualState

  <TextBlock x:Name="KBMIcon" noesis:RichText.Text="[input]AimAbilityConfirm[/input]"/>

Broken — starts Collapsed, RichText never processes when made Visible

  <TextBlock x:Name="ControllerIcon" Visibility="Collapsed" noesis:RichText.Text="[input]AimAbilityCancel[/input]"/>

Works — Hidden instead of Collapsed

  <TextBlock x:Name="ControllerIcon" Visibility="Hidden" noesis:RichText.Text="[input]AimAbilityCancel[/input]"/>

...the VisualState that shows the controller icon:

  <VisualState x:Name="Controller">
      <Storyboard>
          <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ControllerIcon"
              Storyboard.TargetProperty="(UIElement.Visibility)">
              <DiscreteObjectKeyFrame KeyTime="0" Value="{x:Static Visibility.Visible}"/>
          </ObjectAnimationUsingKeyFrames>
      </Storyboard>
  </VisualState>

Note: '[input]' is our handler for TryCreateTagExtension

  namespace Runtime.Client.UI.Utilities
  {
      public static class CustomRichTextTags
      {
          public static void Initialize()
          {
              RichText.TryCreateTagExtension = TryCreateTagExtension;
          }

          private static bool TryCreateTagExtension(string tagName, string content,
              List<RichText.Parameter> parameters, InlineCollection inlineCollection)
          {
              switch (tagName)
              {
                  case "input":
                      return ProcessInputRichTag(ref content, ref parameters, ref inlineCollection);
                  // ... other tags ...
              }
          }

          private static bool ProcessInputRichTag(ref string content,
              ref List<RichText.Parameter> parameters, ref InlineCollection inlineCollection)
          {
              var mapCategory = string.Empty;
              var ruleset = string.Empty;
              foreach (var element in parameters)
              {
                  switch (element.Key)
                  {
                      case "ruleset": ruleset = element.Value; break;
                      case "map": mapCategory = element.Value; break;
                  }
              }

              var glyph = new InputActionGlyph
              {
                  MapCategory = mapCategory,
                  RuleSet = ruleset,
                  Action = content
              };
              // ...adds glyph as InlineUIContainer to inlineCollection
          }
      }
  }