Some templates, such as {{val}} on English Wikipedia, output hidden sortkeys. For example, {{val|1110}} outputs:

<span class="nowrap"><span style="display:none" class="sortkey">7003111000000000000♠</span>1110</span>

TextExtracts should ideally strip or ignore the hidden span, but instead it converts it into a displayed span:

<span><span>7003111000000000000♠</span>1110</span>

See for example: https://en.wikipedia.org/w/api.php?action=query&prop=extracts&exchars=200&titles=50000%20Quaoar