Commenting
Creating a comment
Outline supports commenting on the document level and on selections of text, a new icon appears at the end of the formatting toolbar to add a comment once you have selected some text content in the editor. Text that has a linked comment thread appears as a blue underline.

Commenting in the formatting toolbar
You can create a document-level comment by opening the comments sidebar from the button underneath the title, the document menu, or the command menu. There is a comment input at the bottom of the sidebar.
Tip: comments are not visible in publicly shared documents, so you can use them to privately discuss published content.
Replies
Comments support a single level of nested replies. Click on an existing comment or click on the text that was commented on in the document to focus the thread and see the option to reply.
When you leave a reply other team members that have participated in the comment thread will receive a notification.
Reactions
You can leave emoji reactions to any comment, they will appear for everyone in the workspace. Simply click on the smiley face icon that appears on every comment.
To view a list of all reactions and the users that have reacted to a comment you can also access via the “…” → “View Reactions” menu.
Resolving comments
Comments can be resolved from the sidebar, click on the “…” on the first comment in any thread and select “Mark as resolved” to hide the thread from view. Any user that has permission to write comments in the document also has permission to resolve a thread.
Resolved comment threads can be accessed from the checkmark icon in the top right of the sidebar, here you can also unresolve if the conversation needs to continue.

Find resolved comment threads here
Mentions

Mentioning in a document
To mention another user directly you can use the @
syntax which will bring up a list of team members, keep typing to filter the list. You can mention team members in both documents and comments and they will receive a notification.
Formatting
Comments support a subset of formatting options – bold, italic, underlines, links, strikethroughs, and inline code are all available. You can also upload images by pasting them into a comment and insert emoji with the :
shortcut.