From v8.2.0, it is possible to add plain-text textual comments to individual links. For instance, this may be a comment about the purpose or intent of the link. The comments can only be seen in the following pop-overs or stand-alone dialogs:
All the above have an additional box allowing display of the (optional) link comment for the currently selected link. The box also allows the addition/editing/deletion of link comments.
Link comments are plain text; styling of text (bold, italic, etc.) in not supported. Line breaks, e.g. to make paragraphs, are allowed. Use the Return (↩) key in dialogs but in pop-overs, such as Browse Links, it is necessary to use Option+Return (⌥+↩) as the Return key alone will close the pop-over.
Link comments can be accessed only via the UI elements listed above and cannot be accessed via automation, such as action or export code.