The problem with highlighting like one would do in progressive summarization is that it is very easy to accumulate these highlights but not process them into evergreens. It can be so easy that it can be addicting to simply collect them. But we should avoid collecting information.

Highlighting as taught by Tiago Forte encourages information hoarding. It is also time-consuming and expensive to implement (it requires subscriptions to Readwise, Instapaper, and Liner).

References

Ahrens, S. (2017). How to Take Smart Notes: One Simple Technique to Boost Writing, Learning and Thinking – for Students, Academics and Nonfiction Book Writers. CreateSpace Independent Publishing Platform.