What's the most malicious thing you can do with an injected HTML heading element?

A bit of a thought experiment - similar to my Minimum Viable XSS and SVG injection investigations. I recently found a popular website which echoed back user input. It correctly sanitised < to < to prevent any HTML injection. Except… It let through <h2> elements unaltered! Why? I suspect because the output was: <h2>Your search […]
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