"What's the problem?"

ON English Wikisource there is template : https://en.wikisource.org/wiki/Template:Sinogram
which is used to inline using an image an otherwise unsupported character..

The documentation for this contains the following entry:-
": RESULT: {{sinogram|description=⿰火乚|variantof=炸|comment=not in Unicode}}"

The documentation page was showing up on Special:LintErrors ; https://en.wikisource.org/w/index.php?title=Template:Sinogram/doc&action=edit&lintid=529985

So I took the code line into Special:ExpandTemplates

And got the following raw output...:-

<div class="mw-parser-output"><dl><dd> RESULT: <span style="cursor:help;border-bottom:thin dotted red;" title="variant of 炸;not in Unicode"></dd></dl>
<p>⿰火乚
</span>
</p></div>

which is badly formed.

"What was expected?"

The expected behavior was that the Template output was wrapped inside the DD/DL element. and not pushed into it's own <p></p>.