lukaiser

ILAnnotations allows you to select a text in a blog post and add your comment to it. 
The plugin uses the standard comments engine of WordPress, so all other comment plugins should work just fine with it. 
Shortcodes are used to mark the highlighted text. This allows you to still edit a post and move stuff around without losing the annotations.

ILAnnotations

Annotate any text in a blog post and add a comment to it.

mark@edithuddle

Edit Huddle places a the “Fix It”-button on your blog, allowing your readers to highlight and submit corrections to you directly, rather than posting them publicly in your comments section.

Edit Huddle

Your readers are your most powerful editors! Add Edit Huddle to your blog and start receiving corrections from your readers.

ILAnnotations vs Edit Huddle