This feature works with web articles.

How to use it
- Open a saved article and click Comments in the upper-right corner. Supported webpages also offer in-page comments.
- Select article text to save a quote or add a comment.
- Reply under an existing quote or comment.
Press Ctrl/⌘ + Enter to submit a comment.
Deleting the first item in a comment group removes the whole group. Deleting a reply removes only that reply.
Formatting
Comments support common Markdown and math formulas (inline $...$, display $$...$$).
Markdown image syntax does not upload images as comment attachments.