Backport #34745 by MaxWebZ
When adding a link using the "Add a link" button in comment editor,
pasting a URL resulted in incorrect Markdown formatting (double
brackets) instead of replacing the placeholder text.
This fix adds a context check to prevent creating a new markdown link
when we're already inside an existing one.
Fixes#34740
Co-authored-by: MaxWebZ <5054326@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
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