"Standoff" markup is placed outside of the text it is meant to tag. The markup points to rather than wraps the text. org-noter is an example!
Advantages:
One major challenge is robust anchoring. What do you do when the underlying text changes? How do you refer to the "thing" without naming it?
Another problem is that overlapping annotations don't readily linearize - representing multiple standoff markups at once in a single, say, XML document is not straightforward.
Seems to me there's something very Clojure about the idea… keep the underlying data as simple as possible, and let the operations on the data get complex if they need to