The new inline comment functionality recently upgraded in Confluence doesn't seem to work with Excerpt Include blocks of text.
Attempting to comment content that is part of an Excerpt responds with the error message
We can't add your inline comment; the section you highlighted may contain a macro or user mention. Try highlighting plain text.
I'd prefer it operate so that commented selections are maintained with the text and page associated to the Excerpt block. Comments should be visible and accessible on all Excerpt Include references to the original content.
This adds high value when you are showing a collection of excerpts on a centralized page and soliciting feedback from a particular audience.