Unexpected HTML paste when copying code from Gitea

[silverwind]

Originally reported in https://github.com/go-gitea/gitea/issues/22622. To reproduce:

• Open this source file, select all code lines, copy them
• Paste into GitHub comment box
• Pasted content is completely mangled. Paste result below. Expectation would be to only paste the plaintext parts of the clipboard data.

---

{
--


<code class="code-inner"><span class="p">}</span>
</code>