I've noticed a lot of people commenting when they see possible duplicates. Should I do that in addition to flagging or instead of it?
There are two reasons why such comments appear:
They voted to close as a duplicate - The system will then automatically add a comment on their behalf pointing out what other question they consider to be the master or canonical.
They want to see what others think - Either they're unsure of the duplicate or they don't have the voting rights and leave it there for users with 3k to vote on as such.
In most cases, you're probably seeing the first instance triggered.
In the second case, it's always helpful to point out possible duplicate leads and users who do have vote to close privileges can carry it through.
If you're under the 3k threshold you can still throw in with:
- Leave a comment for others to pick up on and vote on your behalf if they agree
- Dropping the link in the Vote to Close room
- Flag the question pointing out which question it should be closed as a duplicate of.