01
Anchored to the text
Highlight a phrase and comment on exactly that. The quote travels with the thread, so nobody has to ask which part you meant.
02
Threads, not a pile
Replies stay under the comment they answer, in the margin beside the text. A long discussion never buries the document it is about.
03
Resolve when it is settled
Close a thread and it leaves the margin without leaving the record. Reopen it whenever the question comes back.
04
On tasks too
The same threads work on a task description, so a decision is recorded where the work is, not in a chat somebody has to search.
Stop explaining which paragraph
Select the sentence, leave the comment, and let the note carry the conversation.