This usually means that the user mixed up our lowercase/uppercase naming convention; see https://github.com/facebook/react/pull/3429#issuecomment-85166440.

We could add a message like

> Warning: The tag <commentBox> is unrecognized in this browser. If you meant to render a React component, start its name with an uppercase letter.

We'd check this only once per tag and only in development mode.

return <FancyTable><FancyRow /></FancyTable>;
      }
      function App2() {
        return <Viz2 />;
      }
      ReactTestUtils.renderIntoDocument(<App2 />);
      expectDev(console.error.calls.count()).toBe(2);
      expectDev(
        normalizeCodeLocInfo(console.error.calls.argsFor(1)[0]),
      ).toContain(
        ReactDOMFeatureFlags.useFiber
          ? '\n    in tr (at **)' +
              '\n    in Row (at **)' +
              '\n    in FancyRow (at **)' +
              '\n    in table (at **)' +
              '\n    in Table (at **)' +
              '\n    in FancyTable (at **)' +
              '\n    in Viz2 (at **)'
          : 'See Viz2 > FancyTable > Table > table > FancyRow > Row > tr.',
      );
      ReactTestUtils.renderIntoDocument(<FancyTable><FancyRow /></FancyTable>);
      expectDev(console.error.calls.count()).toBe(3);
      expectDev(
        normalizeCodeLocInfo(console.error.calls.argsFor(2)[0]),
      ).toContain(
        ReactDOMFeatureFlags.useFiber
          ? '\n    in tr (at **)' +
              '\n    in Row (at **)' +
              '\n    in FancyRow (at **)' +